diff --git a/rename.js b/rename.js
new file mode 100644
index 0000000000..ad3804e39d
--- /dev/null
+++ b/rename.js
@@ -0,0 +1,9 @@
+const glob = require( 'glob' );
+const fs = require( 'fs' );
+
+glob.sync( 'src/**/*.js' ).forEach( file => {
+	console.log( file );
+	const js = fs.readFileSync( file, 'utf-8' );
+	fs.writeFileSync( file.replace( /\.js$/, '.ts' ), js );
+	fs.unlinkSync( file );
+});
\ No newline at end of file
diff --git a/src/generators/Generator.js b/src/generators/Generator.ts
similarity index 96%
rename from src/generators/Generator.js
rename to src/generators/Generator.ts
index 7a316adc85..c854806f5b 100644
--- a/src/generators/Generator.js
+++ b/src/generators/Generator.ts
@@ -1,15 +1,15 @@
 import MagicString, { Bundle } from 'magic-string';
 import { walk } from 'estree-walker';
-import isReference from '../utils/isReference.js';
-import flattenReference from '../utils/flattenReference.js';
-import globalWhitelist from '../utils/globalWhitelist.js';
-import reservedNames from '../utils/reservedNames.js';
-import namespaces from '../utils/namespaces.js';
-import { removeNode, removeObjectKey } from '../utils/removeNode.js';
-import getIntro from './shared/utils/getIntro.js';
-import getOutro from './shared/utils/getOutro.js';
-import processCss from './shared/processCss.js';
-import annotateWithScopes from '../utils/annotateWithScopes.js';
+import isReference from '../utils/isReference.ts';
+import flattenReference from '../utils/flattenReference.ts';
+import globalWhitelist from '../utils/globalWhitelist.ts';
+import reservedNames from '../utils/reservedNames.ts';
+import namespaces from '../utils/namespaces.ts';
+import { removeNode, removeObjectKey } from '../utils/removeNode.ts';
+import getIntro from './shared/utils/getIntro.ts';
+import getOutro from './shared/utils/getOutro.ts';
+import processCss from './shared/processCss.ts';
+import annotateWithScopes from '../utils/annotateWithScopes.ts';
 
 const test = typeof global !== 'undefined' && global.__svelte_test;
 
@@ -39,7 +39,7 @@ export default class Generator {
 		this.usesRefs = false;
 
 		// allow compiler to deconflict user's `import { get } from 'whatever'` and
-		// Svelte's builtin `import { get, ... } from 'svelte/shared.js'`;
+		// Svelte's builtin `import { get, ... } from 'svelte/shared.ts'`;
 		this.importedNames = new Set();
 		this.aliases = new Map();
 		this._usedNames = new Set( [ name ] );
diff --git a/src/generators/dom/Block.js b/src/generators/dom/Block.ts
similarity index 99%
rename from src/generators/dom/Block.js
rename to src/generators/dom/Block.ts
index 83841b738d..a7775bd355 100644
--- a/src/generators/dom/Block.js
+++ b/src/generators/dom/Block.ts
@@ -1,4 +1,4 @@
-import CodeBuilder from '../../utils/CodeBuilder.js';
+import CodeBuilder from '../../utils/CodeBuilder.ts';
 import deindent from '../../utils/deindent.js';
 
 export default class Block {
diff --git a/src/generators/dom/index.js b/src/generators/dom/index.ts
similarity index 96%
rename from src/generators/dom/index.js
rename to src/generators/dom/index.ts
index cb331fd96a..e4fa2c6f71 100644
--- a/src/generators/dom/index.js
+++ b/src/generators/dom/index.ts
@@ -1,14 +1,14 @@
 import MagicString from 'magic-string';
 import { parseExpressionAt } from 'acorn';
-import annotateWithScopes from '../../utils/annotateWithScopes.js';
-import isReference from '../../utils/isReference.js';
+import annotateWithScopes from '../../utils/annotateWithScopes.ts';
+import isReference from '../../utils/isReference.ts';
 import { walk } from 'estree-walker';
 import deindent from '../../utils/deindent.js';
-import CodeBuilder from '../../utils/CodeBuilder.js';
-import visit from './visit.js';
-import shared from './shared.js';
-import Generator from '../Generator.js';
-import preprocess from './preprocess.js';
+import CodeBuilder from '../../utils/CodeBuilder.ts';
+import visit from './visit.ts';
+import shared from './shared.ts';
+import Generator from '../Generator.ts';
+import preprocess from './preprocess.ts';
 
 class DomGenerator extends Generator {
 	constructor ( parsed, source, name, options ) {
diff --git a/src/generators/dom/preprocess.js b/src/generators/dom/preprocess.ts
similarity index 98%
rename from src/generators/dom/preprocess.js
rename to src/generators/dom/preprocess.ts
index 522a682074..0de5c21040 100644
--- a/src/generators/dom/preprocess.js
+++ b/src/generators/dom/preprocess.ts
@@ -1,5 +1,5 @@
-import Block from './Block.js';
-import { trimStart, trimEnd } from '../../utils/trim.js';
+import Block from './Block.ts';
+import { trimStart, trimEnd } from '../../utils/trim.ts';
 import { assign } from '../../shared/index.js';
 
 function isElseIf ( node ) {
diff --git a/src/generators/dom/shared.ts b/src/generators/dom/shared.ts
new file mode 100644
index 0000000000..a368a0e580
--- /dev/null
+++ b/src/generators/dom/shared.ts
@@ -0,0 +1,35 @@
+// this file is auto-generated, do not edit it
+export default {
+	"appendNode": "function appendNode ( node, target ) {\n\ttarget.appendChild( node );\n}",
+	"insertNode": "function insertNode ( node, target, anchor ) {\n\ttarget.insertBefore( node, anchor );\n}",
+	"detachNode": "function detachNode ( node ) {\n\tnode.parentNode.removeChild( node );\n}",
+	"detachBetween": "function detachBetween ( before, after ) {\n\twhile ( before.nextSibling && before.nextSibling !== after ) {\n\t\tbefore.parentNode.removeChild( before.nextSibling );\n\t}\n}",
+	"destroyEach": "function destroyEach ( iterations, detach, start ) {\n\tfor ( var i = start; i < iterations.length; i += 1 ) {\n\t\tif ( iterations[i] ) iterations[i].destroy( detach );\n\t}\n}",
+	"createElement": "function createElement ( name ) {\n\treturn document.createElement( name );\n}",
+	"createSvgElement": "function createSvgElement ( name ) {\n\treturn document.createElementNS( 'http://www.w3.org/2000/svg', name );\n}",
+	"createText": "function createText ( data ) {\n\treturn document.createTextNode( data );\n}",
+	"createComment": "function createComment () {\n\treturn document.createComment( '' );\n}",
+	"addEventListener": "function addEventListener ( node, event, handler ) {\n\tnode.addEventListener( event, handler, false );\n}",
+	"removeEventListener": "function removeEventListener ( node, event, handler ) {\n\tnode.removeEventListener( event, handler, false );\n}",
+	"setAttribute": "function setAttribute ( node, attribute, value ) {\n\tnode.setAttribute( attribute, value );\n}",
+	"setXlinkAttribute": "function setXlinkAttribute ( node, attribute, value ) {\n\tnode.setAttributeNS( 'http://www.w3.org/1999/xlink', attribute, value );\n}",
+	"getBindingGroupValue": "function getBindingGroupValue ( group ) {\n\tvar value = [];\n\tfor ( var i = 0; i < group.length; i += 1 ) {\n\t\tif ( group[i].checked ) value.push( group[i].__value );\n\t}\n\treturn value;\n}",
+	"differs": "function differs ( a, b ) {\n\treturn ( a !== b ) || ( a && ( typeof a === 'object' ) || ( typeof a === 'function' ) );\n}",
+	"dispatchObservers": "function dispatchObservers ( component, group, newState, oldState ) {\n\tfor ( var key in group ) {\n\t\tif ( !( key in newState ) ) continue;\n\n\t\tvar newValue = newState[ key ];\n\t\tvar oldValue = oldState[ key ];\n\n\t\tif ( differs( newValue, oldValue ) ) {\n\t\t\tvar callbacks = group[ key ];\n\t\t\tif ( !callbacks ) continue;\n\n\t\t\tfor ( var i = 0; i < callbacks.length; i += 1 ) {\n\t\t\t\tvar callback = callbacks[i];\n\t\t\t\tif ( callback.__calling ) continue;\n\n\t\t\t\tcallback.__calling = true;\n\t\t\t\tcallback.call( component, newValue, oldValue );\n\t\t\t\tcallback.__calling = false;\n\t\t\t}\n\t\t}\n\t}\n}",
+	"get": "function get ( key ) {\n\treturn key ? this._state[ key ] : this._state;\n}",
+	"fire": "function fire ( eventName, data ) {\n\tvar handlers = eventName in this._handlers && this._handlers[ eventName ].slice();\n\tif ( !handlers ) return;\n\n\tfor ( var i = 0; i < handlers.length; i += 1 ) {\n\t\thandlers[i].call( this, data );\n\t}\n}",
+	"observe": "function observe ( key, callback, options ) {\n\tvar group = ( options && options.defer ) ? this._observers.post : this._observers.pre;\n\n\t( group[ key ] || ( group[ key ] = [] ) ).push( callback );\n\n\tif ( !options || options.init !== false ) {\n\t\tcallback.__calling = true;\n\t\tcallback.call( this, this._state[ key ] );\n\t\tcallback.__calling = false;\n\t}\n\n\treturn {\n\t\tcancel: function () {\n\t\t\tvar index = group[ key ].indexOf( callback );\n\t\t\tif ( ~index ) group[ key ].splice( index, 1 );\n\t\t}\n\t};\n}",
+	"observeDev": "function observeDev ( key, callback, options ) {\n\tvar c = ( key = '' + key ).search( /[^\\w]/ );\n\tif ( c > -1 ) {\n\t\tvar message = \"The first argument to component.observe(...) must be the name of a top-level property\";\n\t\tif ( c > 0 ) message += \", i.e. '\" + key.slice( 0, c ) + \"' rather than '\" + key + \"'\";\n\n\t\tthrow new Error( message );\n\t}\n\n\treturn observe.call( this, key, callback, options );\n}",
+	"on": "function on ( eventName, handler ) {\n\tif ( eventName === 'teardown' ) return this.on( 'destroy', handler );\n\n\tvar handlers = this._handlers[ eventName ] || ( this._handlers[ eventName ] = [] );\n\thandlers.push( handler );\n\n\treturn {\n\t\tcancel: function () {\n\t\t\tvar index = handlers.indexOf( handler );\n\t\t\tif ( ~index ) handlers.splice( index, 1 );\n\t\t}\n\t};\n}",
+	"onDev": "function onDev ( eventName, handler ) {\n\tif ( eventName === 'teardown' ) {\n\t\tconsole.warn( \"Use component.on('destroy', ...) instead of component.on('teardown', ...) which has been deprecated and will be unsupported in Svelte 2\" );\n\t\treturn this.on( 'destroy', handler );\n\t}\n\n\treturn on.call( this, eventName, handler );\n}",
+	"set": "function set ( newState ) {\n\tthis._set( assign( {}, newState ) );\n\tthis._root._flush();\n}",
+	"_flush": "function _flush () {\n\tif ( !this._renderHooks ) return;\n\n\twhile ( this._renderHooks.length ) {\n\t\tthis._renderHooks.pop()();\n\t}\n}",
+	"proto": "{\n\tget: get,\n\tfire: fire,\n\tobserve: observe,\n\ton: on,\n\tset: set,\n\t_flush: _flush\n}",
+	"protoDev": "{\n\tget: get,\n\tfire: fire,\n\tobserve: observeDev,\n\ton: onDev,\n\tset: set,\n\t_flush: _flush\n}",
+	"linear": "function linear ( t ) {\n\treturn t;\n}",
+	"generateKeyframes": "function generateKeyframes ( a, b, delta, duration, ease, fn, node, style ) {\n\tvar id = '__svelte' + ~~( Math.random() * 1e9 ); // TODO make this more robust\n\tvar keyframes = '@keyframes ' + id + '{\\n';\n\n\tfor ( var p = 0; p <= 1; p += 16.666 / duration ) {\n\t\tvar t = a + delta * ease( p );\n\t\tkeyframes += ( p * 100 ) + '%{' + fn( t ) + '}\\n';\n\t}\n\n\tkeyframes += '100% {' + fn( b ) + '}\\n}';\n\tstyle.textContent += keyframes;\n\n\tdocument.head.appendChild( style );\n\n\tnode.style.animation = node.style.animation.split( ',' )\n\t\t.filter( function ( anim ) {\n\t\t\t// when introing, discard old animations if there are any\n\t\t\treturn anim && ( delta < 0 || !/__svelte/.test( anim ) );\n\t\t})\n\t\t.concat( id + ' ' + duration + 'ms linear 1 forwards' )\n\t\t.join( ', ' );\n}",
+	"wrapTransition": "function wrapTransition ( node, fn, params, intro, outgroup ) {\n\tvar obj = fn( node, params );\n\tvar duration = obj.duration || 300;\n\tvar ease = obj.easing || linear;\n\n\t// TODO share <style> tag between all transitions?\n\tif ( obj.css ) {\n\t\tvar style = document.createElement( 'style' );\n\t}\n\n\tif ( intro && obj.tick ) obj.tick( 0 );\n\n\treturn {\n\t\tt: intro ? 0 : 1,\n\t\trunning: false,\n\t\tprogram: null,\n\t\tpending: null,\n\t\trun: function ( intro, callback ) {\n\t\t\tvar program = {\n\t\t\t\tstart: window.performance.now() + ( obj.delay || 0 ),\n\t\t\t\tintro: intro,\n\t\t\t\tcallback: callback\n\t\t\t};\n\n\t\t\tif ( obj.delay ) {\n\t\t\t\tthis.pending = program;\n\t\t\t} else {\n\t\t\t\tthis.start( program );\n\t\t\t}\n\n\t\t\tif ( !this.running ) {\n\t\t\t\tthis.running = true;\n\t\t\t\ttransitionManager.add( this );\n\t\t\t}\n\t\t},\n\t\tstart: function ( program ) {\n\t\t\tprogram.a = this.t;\n\t\t\tprogram.b = program.intro ? 1 : 0;\n\t\t\tprogram.delta = program.b - program.a;\n\t\t\tprogram.duration = duration * Math.abs( program.b - program.a );\n\t\t\tprogram.end = program.start + program.duration;\n\n\t\t\tif ( obj.css ) {\n\t\t\t\tgenerateKeyframes( program.a, program.b, program.delta, program.duration, ease, obj.css, node, style );\n\t\t\t}\n\n\t\t\tthis.program = program;\n\t\t\tthis.pending = null;\n\t\t},\n\t\tupdate: function ( now ) {\n\t\t\tvar program = this.program;\n\t\t\tif ( !program ) return;\n\n\t\t\tvar p = now - program.start;\n\t\t\tthis.t = program.a + program.delta * ease( p / program.duration );\n\t\t\tif ( obj.tick ) obj.tick( this.t );\n\t\t},\n\t\tdone: function () {\n\t\t\tthis.t = this.program.b;\n\t\t\tif ( obj.tick ) obj.tick( this.t );\n\t\t\tif ( obj.css ) document.head.removeChild( style );\n\t\t\tthis.program.callback();\n\t\t\tthis.program = null;\n\t\t\tthis.running = !!this.pending;\n\t\t},\n\t\tabort: function () {\n\t\t\tif ( obj.tick ) obj.tick( 1 );\n\t\t\tif ( obj.css ) document.head.removeChild( style );\n\t\t\tthis.program = this.pending = null;\n\t\t\tthis.running = false;\n\t\t}\n\t};\n}",
+	"transitionManager": "{\n\trunning: false,\n\ttransitions: [],\n\n\tadd: function ( transition ) {\n\t\ttransitionManager.transitions.push( transition );\n\n\t\tif ( !this.running ) {\n\t\t\tthis.running = true;\n\t\t\tthis.next();\n\t\t}\n\t},\n\n\tnext: function () {\n\t\ttransitionManager.running = false;\n\n\t\tvar now = window.performance.now();\n\t\tvar i = transitionManager.transitions.length;\n\n\t\twhile ( i-- ) {\n\t\t\tvar transition = transitionManager.transitions[i];\n\n\t\t\tif ( transition.program && now >= transition.program.end ) {\n\t\t\t\ttransition.done();\n\t\t\t}\n\n\t\t\tif ( transition.pending && now >= transition.pending.start ) {\n\t\t\t\ttransition.start( transition.pending );\n\t\t\t}\n\n\t\t\tif ( transition.running ) {\n\t\t\t\ttransition.update( now );\n\t\t\t\ttransitionManager.running = true;\n\t\t\t} else if ( !transition.pending ) {\n\t\t\t\ttransitionManager.transitions.splice( i, 1 );\n\t\t\t}\n\t\t}\n\n\t\tif ( transitionManager.running ) {\n\t\t\trequestAnimationFrame( transitionManager.next );\n\t\t}\n\t}\n}",
+	"noop": "function noop () {}",
+	"assign": "function assign ( target ) {\n\tfor ( var i = 1; i < arguments.length; i += 1 ) {\n\t\tvar source = arguments[i];\n\t\tfor ( var k in source ) target[k] = source[k];\n\t}\n\n\treturn target;\n}"
+};
\ No newline at end of file
diff --git a/src/generators/dom/visit.js b/src/generators/dom/visit.ts
similarity index 76%
rename from src/generators/dom/visit.js
rename to src/generators/dom/visit.ts
index 22a040af06..fc1f539f50 100644
--- a/src/generators/dom/visit.js
+++ b/src/generators/dom/visit.ts
@@ -1,4 +1,4 @@
-import visitors from './visitors/index.js';
+import visitors from './visitors/index.ts';
 
 export default function visit ( generator, block, state, node ) {
 	const visitor = visitors[ node.type ];
diff --git a/src/generators/dom/visitors/Component/Attribute.js b/src/generators/dom/visitors/Component/Attribute.ts
similarity index 100%
rename from src/generators/dom/visitors/Component/Attribute.js
rename to src/generators/dom/visitors/Component/Attribute.ts
diff --git a/src/generators/dom/visitors/Component/Binding.js b/src/generators/dom/visitors/Component/Binding.ts
similarity index 97%
rename from src/generators/dom/visitors/Component/Binding.js
rename to src/generators/dom/visitors/Component/Binding.ts
index 9465eca810..4339f38697 100644
--- a/src/generators/dom/visitors/Component/Binding.js
+++ b/src/generators/dom/visitors/Component/Binding.ts
@@ -1,6 +1,6 @@
 import deindent from '../../../../utils/deindent.js';
-import flattenReference from '../../../../utils/flattenReference.js';
-import getSetter from '../shared/binding/getSetter.js';
+import flattenReference from '../../../../utils/flattenReference.ts';
+import getSetter from '../shared/binding/getSetter.ts';
 
 export default function visitBinding ( generator, block, state, node, attribute, local ) {
 	const { name } = flattenReference( attribute.value );
diff --git a/src/generators/dom/visitors/Component/Component.js b/src/generators/dom/visitors/Component/Component.ts
similarity index 95%
rename from src/generators/dom/visitors/Component/Component.js
rename to src/generators/dom/visitors/Component/Component.ts
index e4685cf9dd..a74af5f8fe 100644
--- a/src/generators/dom/visitors/Component/Component.js
+++ b/src/generators/dom/visitors/Component/Component.ts
@@ -1,10 +1,10 @@
 import deindent from '../../../../utils/deindent.js';
-import CodeBuilder from '../../../../utils/CodeBuilder.js';
-import visit from '../../visit.js';
-import visitAttribute from './Attribute.js';
-import visitEventHandler from './EventHandler.js';
-import visitBinding from './Binding.js';
-import visitRef from './Ref.js';
+import CodeBuilder from '../../../../utils/CodeBuilder.ts';
+import visit from '../../visit.ts';
+import visitAttribute from './Attribute.ts';
+import visitEventHandler from './EventHandler.ts';
+import visitBinding from './Binding.ts';
+import visitRef from './Ref.ts';
 
 function stringifyProps ( props ) {
 	if ( !props.length ) return '{}';
diff --git a/src/generators/dom/visitors/Component/EventHandler.js b/src/generators/dom/visitors/Component/EventHandler.ts
similarity index 100%
rename from src/generators/dom/visitors/Component/EventHandler.js
rename to src/generators/dom/visitors/Component/EventHandler.ts
diff --git a/src/generators/dom/visitors/Component/Ref.js b/src/generators/dom/visitors/Component/Ref.ts
similarity index 100%
rename from src/generators/dom/visitors/Component/Ref.js
rename to src/generators/dom/visitors/Component/Ref.ts
diff --git a/src/generators/dom/visitors/EachBlock.js b/src/generators/dom/visitors/EachBlock.ts
similarity index 99%
rename from src/generators/dom/visitors/EachBlock.js
rename to src/generators/dom/visitors/EachBlock.ts
index d30406598c..1834f35bc3 100644
--- a/src/generators/dom/visitors/EachBlock.js
+++ b/src/generators/dom/visitors/EachBlock.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../utils/deindent.js';
-import visit from '../visit.js';
+import visit from '../visit.ts';
 
 export default function visitEachBlock ( generator, block, state, node ) {
 	const each_block = generator.getUniqueName( `each_block` );
diff --git a/src/generators/dom/visitors/Element/Attribute.js b/src/generators/dom/visitors/Element/Attribute.ts
similarity index 97%
rename from src/generators/dom/visitors/Element/Attribute.js
rename to src/generators/dom/visitors/Element/Attribute.ts
index 1e83b5d33e..1457d00698 100644
--- a/src/generators/dom/visitors/Element/Attribute.js
+++ b/src/generators/dom/visitors/Element/Attribute.ts
@@ -1,6 +1,6 @@
-import attributeLookup from './lookup.js';
+import attributeLookup from './lookup.ts';
 import deindent from '../../../../utils/deindent.js';
-import getStaticAttributeValue from './getStaticAttributeValue.js';
+import getStaticAttributeValue from './getStaticAttributeValue.ts';
 
 export default function visitAttribute ( generator, block, state, node, attribute ) {
 	const name = attribute.name;
diff --git a/src/generators/dom/visitors/Element/Binding.js b/src/generators/dom/visitors/Element/Binding.ts
similarity index 98%
rename from src/generators/dom/visitors/Element/Binding.js
rename to src/generators/dom/visitors/Element/Binding.ts
index 83d415cb74..ddf978dbbd 100644
--- a/src/generators/dom/visitors/Element/Binding.js
+++ b/src/generators/dom/visitors/Element/Binding.ts
@@ -1,7 +1,7 @@
 import deindent from '../../../../utils/deindent.js';
-import flattenReference from '../../../../utils/flattenReference.js';
-import getSetter from '../shared/binding/getSetter.js';
-import getStaticAttributeValue from './getStaticAttributeValue.js';
+import flattenReference from '../../../../utils/flattenReference.ts';
+import getSetter from '../shared/binding/getSetter.ts';
+import getStaticAttributeValue from './getStaticAttributeValue.ts';
 
 export default function visitBinding ( generator, block, state, node, attribute ) {
 	const { name, parts } = flattenReference( attribute.value );
diff --git a/src/generators/dom/visitors/Element/Element.js b/src/generators/dom/visitors/Element/Element.ts
similarity index 91%
rename from src/generators/dom/visitors/Element/Element.js
rename to src/generators/dom/visitors/Element/Element.ts
index bdf408732f..17bf3f396b 100644
--- a/src/generators/dom/visitors/Element/Element.js
+++ b/src/generators/dom/visitors/Element/Element.ts
@@ -1,12 +1,12 @@
 import deindent from '../../../../utils/deindent.js';
-import visit from '../../visit.js';
-import visitComponent from '../Component/Component.js';
-import visitWindow from './meta/Window.js';
-import visitAttribute from './Attribute.js';
-import visitEventHandler from './EventHandler.js';
-import visitBinding from './Binding.js';
-import visitRef from './Ref.js';
-import addTransitions from './addTransitions.js';
+import visit from '../../visit.ts';
+import visitComponent from '../Component/Component.ts';
+import visitWindow from './meta/Window.ts';
+import visitAttribute from './Attribute.ts';
+import visitEventHandler from './EventHandler.ts';
+import visitBinding from './Binding.ts';
+import visitRef from './Ref.ts';
+import addTransitions from './addTransitions.ts';
 
 const meta = {
 	':Window': visitWindow
diff --git a/src/generators/dom/visitors/Element/EventHandler.js b/src/generators/dom/visitors/Element/EventHandler.ts
similarity index 99%
rename from src/generators/dom/visitors/Element/EventHandler.js
rename to src/generators/dom/visitors/Element/EventHandler.ts
index 2979d5d2f9..a5d72131f4 100644
--- a/src/generators/dom/visitors/Element/EventHandler.js
+++ b/src/generators/dom/visitors/Element/EventHandler.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../../utils/deindent.js';
-import flattenReference from '../../../../utils/flattenReference.js';
+import flattenReference from '../../../../utils/flattenReference.ts';
 
 export default function visitEventHandler ( generator, block, state, node, attribute ) {
 	const name = attribute.name;
diff --git a/src/generators/dom/visitors/Element/Ref.js b/src/generators/dom/visitors/Element/Ref.ts
similarity index 100%
rename from src/generators/dom/visitors/Element/Ref.js
rename to src/generators/dom/visitors/Element/Ref.ts
diff --git a/src/generators/dom/visitors/Element/addTransitions.js b/src/generators/dom/visitors/Element/addTransitions.ts
similarity index 100%
rename from src/generators/dom/visitors/Element/addTransitions.js
rename to src/generators/dom/visitors/Element/addTransitions.ts
diff --git a/src/generators/dom/visitors/Element/getStaticAttributeValue.js b/src/generators/dom/visitors/Element/getStaticAttributeValue.ts
similarity index 100%
rename from src/generators/dom/visitors/Element/getStaticAttributeValue.js
rename to src/generators/dom/visitors/Element/getStaticAttributeValue.ts
diff --git a/src/generators/dom/visitors/Element/lookup.js b/src/generators/dom/visitors/Element/lookup.ts
similarity index 100%
rename from src/generators/dom/visitors/Element/lookup.js
rename to src/generators/dom/visitors/Element/lookup.ts
diff --git a/src/generators/dom/visitors/Element/meta/Window.js b/src/generators/dom/visitors/Element/meta/Window.ts
similarity index 99%
rename from src/generators/dom/visitors/Element/meta/Window.js
rename to src/generators/dom/visitors/Element/meta/Window.ts
index 2478d17139..be847abfe9 100644
--- a/src/generators/dom/visitors/Element/meta/Window.js
+++ b/src/generators/dom/visitors/Element/meta/Window.ts
@@ -1,4 +1,4 @@
-import flattenReference from '../../../../../utils/flattenReference.js';
+import flattenReference from '../../../../../utils/flattenReference.ts';
 import deindent from '../../../../../utils/deindent.js';
 
 const associatedEvents = {
diff --git a/src/generators/dom/visitors/IfBlock.js b/src/generators/dom/visitors/IfBlock.ts
similarity index 99%
rename from src/generators/dom/visitors/IfBlock.js
rename to src/generators/dom/visitors/IfBlock.ts
index 05ed1c1481..968cc734b5 100644
--- a/src/generators/dom/visitors/IfBlock.js
+++ b/src/generators/dom/visitors/IfBlock.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../utils/deindent.js';
-import visit from '../visit.js';
+import visit from '../visit.ts';
 
 function isElseIf ( node ) {
 	return node && node.children.length === 1 && node.children[0].type === 'IfBlock';
diff --git a/src/generators/dom/visitors/MustacheTag.js b/src/generators/dom/visitors/MustacheTag.ts
similarity index 100%
rename from src/generators/dom/visitors/MustacheTag.js
rename to src/generators/dom/visitors/MustacheTag.ts
diff --git a/src/generators/dom/visitors/RawMustacheTag.js b/src/generators/dom/visitors/RawMustacheTag.ts
similarity index 100%
rename from src/generators/dom/visitors/RawMustacheTag.js
rename to src/generators/dom/visitors/RawMustacheTag.ts
diff --git a/src/generators/dom/visitors/Text.js b/src/generators/dom/visitors/Text.ts
similarity index 100%
rename from src/generators/dom/visitors/Text.js
rename to src/generators/dom/visitors/Text.ts
diff --git a/src/generators/dom/visitors/YieldTag.js b/src/generators/dom/visitors/YieldTag.ts
similarity index 100%
rename from src/generators/dom/visitors/YieldTag.js
rename to src/generators/dom/visitors/YieldTag.ts
diff --git a/src/generators/dom/visitors/index.js b/src/generators/dom/visitors/index.js
deleted file mode 100644
index 4bdf5b4591..0000000000
--- a/src/generators/dom/visitors/index.js
+++ /dev/null
@@ -1,17 +0,0 @@
-import EachBlock from './EachBlock.js';
-import Element from './Element/Element.js';
-import IfBlock from './IfBlock.js';
-import MustacheTag from './MustacheTag.js';
-import RawMustacheTag from './RawMustacheTag.js';
-import Text from './Text.js';
-import YieldTag from './YieldTag.js';
-
-export default {
-	EachBlock,
-	Element,
-	IfBlock,
-	MustacheTag,
-	RawMustacheTag,
-	Text,
-	YieldTag
-};
diff --git a/src/generators/dom/visitors/index.ts b/src/generators/dom/visitors/index.ts
new file mode 100644
index 0000000000..a6802130ad
--- /dev/null
+++ b/src/generators/dom/visitors/index.ts
@@ -0,0 +1,17 @@
+import EachBlock from './EachBlock.ts';
+import Element from './Element/Element.ts';
+import IfBlock from './IfBlock.ts';
+import MustacheTag from './MustacheTag.ts';
+import RawMustacheTag from './RawMustacheTag.ts';
+import Text from './Text.ts';
+import YieldTag from './YieldTag.ts';
+
+export default {
+	EachBlock,
+	Element,
+	IfBlock,
+	MustacheTag,
+	RawMustacheTag,
+	Text,
+	YieldTag
+};
diff --git a/src/generators/dom/visitors/shared/binding/getSetter.js b/src/generators/dom/visitors/shared/binding/getSetter.ts
similarity index 100%
rename from src/generators/dom/visitors/shared/binding/getSetter.js
rename to src/generators/dom/visitors/shared/binding/getSetter.ts
diff --git a/src/generators/server-side-rendering/Block.js b/src/generators/server-side-rendering/Block.ts
similarity index 92%
rename from src/generators/server-side-rendering/Block.js
rename to src/generators/server-side-rendering/Block.ts
index fa317721e0..3556c6e76a 100644
--- a/src/generators/server-side-rendering/Block.js
+++ b/src/generators/server-side-rendering/Block.ts
@@ -1,5 +1,5 @@
 import deindent from '../../utils/deindent.js';
-import flattenReference from '../../utils/flattenReference.js';
+import flattenReference from '../../utils/flattenReference.ts';
 
 export default class Block {
 	constructor ( options ) {
diff --git a/src/generators/server-side-rendering/index.js b/src/generators/server-side-rendering/index.ts
similarity index 96%
rename from src/generators/server-side-rendering/index.js
rename to src/generators/server-side-rendering/index.ts
index 2b3be31bbd..4cebd26884 100644
--- a/src/generators/server-side-rendering/index.js
+++ b/src/generators/server-side-rendering/index.ts
@@ -1,7 +1,7 @@
 import deindent from '../../utils/deindent.js';
-import Generator from '../Generator.js';
-import Block from './Block.js';
-import visit from './visit.js';
+import Generator from '../Generator.ts';
+import Block from './Block.ts';
+import visit from './visit.ts';
 
 class SsrGenerator extends Generator {
 	constructor ( parsed, source, name, options ) {
diff --git a/src/generators/server-side-rendering/visit.js b/src/generators/server-side-rendering/visit.ts
similarity index 75%
rename from src/generators/server-side-rendering/visit.js
rename to src/generators/server-side-rendering/visit.ts
index 1b96ed510b..74544ce12f 100644
--- a/src/generators/server-side-rendering/visit.js
+++ b/src/generators/server-side-rendering/visit.ts
@@ -1,4 +1,4 @@
-import visitors from './visitors/index.js';
+import visitors from './visitors/index.ts';
 
 export default function visit ( generator, fragment, node ) {
 	const visitor = visitors[ node.type ];
diff --git a/src/generators/server-side-rendering/visitors/Comment.js b/src/generators/server-side-rendering/visitors/Comment.ts
similarity index 100%
rename from src/generators/server-side-rendering/visitors/Comment.js
rename to src/generators/server-side-rendering/visitors/Comment.ts
diff --git a/src/generators/server-side-rendering/visitors/Component.js b/src/generators/server-side-rendering/visitors/Component.ts
similarity index 95%
rename from src/generators/server-side-rendering/visitors/Component.js
rename to src/generators/server-side-rendering/visitors/Component.ts
index 6290ca0710..0ef08968b3 100644
--- a/src/generators/server-side-rendering/visitors/Component.js
+++ b/src/generators/server-side-rendering/visitors/Component.ts
@@ -1,5 +1,5 @@
-import flattenReference from '../../../utils/flattenReference.js';
-import visit from '../visit.js';
+import flattenReference from '../../../utils/flattenReference.ts';
+import visit from '../visit.ts';
 
 export default function visitComponent ( generator, block, node ) {
 	function stringify ( chunk ) {
diff --git a/src/generators/server-side-rendering/visitors/EachBlock.js b/src/generators/server-side-rendering/visitors/EachBlock.ts
similarity index 96%
rename from src/generators/server-side-rendering/visitors/EachBlock.js
rename to src/generators/server-side-rendering/visitors/EachBlock.ts
index b26bbb4222..1e90758047 100644
--- a/src/generators/server-side-rendering/visitors/EachBlock.js
+++ b/src/generators/server-side-rendering/visitors/EachBlock.ts
@@ -1,4 +1,4 @@
-import visit from '../visit.js';
+import visit from '../visit.ts';
 
 export default function visitEachBlock ( generator, block, node ) {
 	const { dependencies, snippet } = block.contextualise( node.expression );
diff --git a/src/generators/server-side-rendering/visitors/Element.js b/src/generators/server-side-rendering/visitors/Element.ts
similarity index 90%
rename from src/generators/server-side-rendering/visitors/Element.js
rename to src/generators/server-side-rendering/visitors/Element.ts
index 0a6c5f42c4..bbc08bb2dd 100644
--- a/src/generators/server-side-rendering/visitors/Element.js
+++ b/src/generators/server-side-rendering/visitors/Element.ts
@@ -1,7 +1,7 @@
-import visitComponent from './Component.js';
-import isVoidElementName from '../../../utils/isVoidElementName.js';
-import visit from '../visit.js';
-import visitWindow from './meta/Window.js';
+import visitComponent from './Component.ts';
+import isVoidElementName from '../../../utils/isVoidElementName.ts';
+import visit from '../visit.ts';
+import visitWindow from './meta/Window.ts';
 
 const meta = {
 	':Window': visitWindow
diff --git a/src/generators/server-side-rendering/visitors/IfBlock.js b/src/generators/server-side-rendering/visitors/IfBlock.ts
similarity index 93%
rename from src/generators/server-side-rendering/visitors/IfBlock.js
rename to src/generators/server-side-rendering/visitors/IfBlock.ts
index eb2af2caae..10355913d8 100644
--- a/src/generators/server-side-rendering/visitors/IfBlock.js
+++ b/src/generators/server-side-rendering/visitors/IfBlock.ts
@@ -1,4 +1,4 @@
-import visit from '../visit.js';
+import visit from '../visit.ts';
 
 export default function visitIfBlock ( generator, block, node ) {
 	const { snippet } = block.contextualise( node.expression );
diff --git a/src/generators/server-side-rendering/visitors/MustacheTag.js b/src/generators/server-side-rendering/visitors/MustacheTag.ts
similarity index 100%
rename from src/generators/server-side-rendering/visitors/MustacheTag.js
rename to src/generators/server-side-rendering/visitors/MustacheTag.ts
diff --git a/src/generators/server-side-rendering/visitors/RawMustacheTag.js b/src/generators/server-side-rendering/visitors/RawMustacheTag.ts
similarity index 100%
rename from src/generators/server-side-rendering/visitors/RawMustacheTag.js
rename to src/generators/server-side-rendering/visitors/RawMustacheTag.ts
diff --git a/src/generators/server-side-rendering/visitors/Text.js b/src/generators/server-side-rendering/visitors/Text.ts
similarity index 100%
rename from src/generators/server-side-rendering/visitors/Text.js
rename to src/generators/server-side-rendering/visitors/Text.ts
diff --git a/src/generators/server-side-rendering/visitors/YieldTag.js b/src/generators/server-side-rendering/visitors/YieldTag.ts
similarity index 100%
rename from src/generators/server-side-rendering/visitors/YieldTag.js
rename to src/generators/server-side-rendering/visitors/YieldTag.ts
diff --git a/src/generators/server-side-rendering/visitors/index.js b/src/generators/server-side-rendering/visitors/index.js
deleted file mode 100644
index 8e125e5d8b..0000000000
--- a/src/generators/server-side-rendering/visitors/index.js
+++ /dev/null
@@ -1,19 +0,0 @@
-import Comment from './Comment.js';
-import EachBlock from './EachBlock.js';
-import Element from './Element.js';
-import IfBlock from './IfBlock.js';
-import MustacheTag from './MustacheTag.js';
-import RawMustacheTag from './RawMustacheTag.js';
-import Text from './Text.js';
-import YieldTag from './YieldTag.js';
-
-export default {
-	Comment,
-	EachBlock,
-	Element,
-	IfBlock,
-	MustacheTag,
-	RawMustacheTag,
-	Text,
-	YieldTag
-};
diff --git a/src/generators/server-side-rendering/visitors/index.ts b/src/generators/server-side-rendering/visitors/index.ts
new file mode 100644
index 0000000000..1067dcf733
--- /dev/null
+++ b/src/generators/server-side-rendering/visitors/index.ts
@@ -0,0 +1,19 @@
+import Comment from './Comment.ts';
+import EachBlock from './EachBlock.ts';
+import Element from './Element.ts';
+import IfBlock from './IfBlock.ts';
+import MustacheTag from './MustacheTag.ts';
+import RawMustacheTag from './RawMustacheTag.ts';
+import Text from './Text.ts';
+import YieldTag from './YieldTag.ts';
+
+export default {
+	Comment,
+	EachBlock,
+	Element,
+	IfBlock,
+	MustacheTag,
+	RawMustacheTag,
+	Text,
+	YieldTag
+};
diff --git a/src/generators/server-side-rendering/visitors/meta/Window.js b/src/generators/server-side-rendering/visitors/meta/Window.ts
similarity index 100%
rename from src/generators/server-side-rendering/visitors/meta/Window.js
rename to src/generators/server-side-rendering/visitors/meta/Window.ts
diff --git a/src/generators/shared/processCss.js b/src/generators/shared/processCss.ts
similarity index 100%
rename from src/generators/shared/processCss.js
rename to src/generators/shared/processCss.ts
diff --git a/src/generators/shared/utils/getGlobals.js b/src/generators/shared/utils/getGlobals.ts
similarity index 100%
rename from src/generators/shared/utils/getGlobals.js
rename to src/generators/shared/utils/getGlobals.ts
diff --git a/src/generators/shared/utils/getIntro.js b/src/generators/shared/utils/getIntro.ts
similarity index 98%
rename from src/generators/shared/utils/getIntro.js
rename to src/generators/shared/utils/getIntro.ts
index c0fa4b4a69..f7c4fcc981 100644
--- a/src/generators/shared/utils/getIntro.js
+++ b/src/generators/shared/utils/getIntro.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../utils/deindent.js';
-import getGlobals from './getGlobals.js';
+import getGlobals from './getGlobals.ts';
 
 export default function getIntro ( format, options, imports ) {
 	if ( format === 'es' ) return '';
diff --git a/src/generators/shared/utils/getOutro.js b/src/generators/shared/utils/getOutro.ts
similarity index 94%
rename from src/generators/shared/utils/getOutro.js
rename to src/generators/shared/utils/getOutro.ts
index 7f7c9354cf..8f2f9004a3 100644
--- a/src/generators/shared/utils/getOutro.js
+++ b/src/generators/shared/utils/getOutro.ts
@@ -1,4 +1,4 @@
-import getGlobals from './getGlobals.js';
+import getGlobals from './getGlobals.ts';
 
 export default function getOutro ( format, name, options, imports ) {
 	if ( format === 'es' ) {
diff --git a/src/generators/shared/utils/walkHtml.js b/src/generators/shared/utils/walkHtml.ts
similarity index 100%
rename from src/generators/shared/utils/walkHtml.js
rename to src/generators/shared/utils/walkHtml.ts
diff --git a/src/index.ts b/src/index.ts
index b9ce974b84..3b1b0a51d0 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,7 @@
 import parse from './parse/index.ts';
-import validate from './validate/index.js';
-import generate from './generators/dom/index.js';
-import generateSSR from './generators/server-side-rendering/index.js';
+import validate from './validate/index.ts';
+import generate from './generators/dom/index.ts';
+import generateSSR from './generators/server-side-rendering/index.ts';
 import { assign } from './shared/index.js';
 import { version } from '../package.json';
 
diff --git a/src/parse/index.ts b/src/parse/index.ts
index fbfa11e4fa..982afb7110 100644
--- a/src/parse/index.ts
+++ b/src/parse/index.ts
@@ -1,8 +1,8 @@
 import { locate } from 'locate-character';
 import fragment from './state/fragment.ts';
-import { whitespace } from '../utils/patterns.js';
-import { trimStart, trimEnd } from '../utils/trim.js';
-import getCodeFrame from '../utils/getCodeFrame.js';
+import { whitespace } from '../utils/patterns.ts';
+import { trimStart, trimEnd } from '../utils/trim.ts';
+import getCodeFrame from '../utils/getCodeFrame.ts';
 import hash from './utils/hash.ts';
 
 function ParseError ( message, template, index, filename ) {
diff --git a/src/parse/state/mustache.ts b/src/parse/state/mustache.ts
index 6eb3431aa0..97781cc9c3 100644
--- a/src/parse/state/mustache.ts
+++ b/src/parse/state/mustache.ts
@@ -1,6 +1,6 @@
 import readExpression from '../read/expression.ts';
-import { whitespace } from '../../utils/patterns.js';
-import { trimStart, trimEnd } from '../../utils/trim.js';
+import { whitespace } from '../../utils/patterns.ts';
+import { trimStart, trimEnd } from '../../utils/trim.ts';
 
 const validIdentifier = /[a-zA-Z_$][a-zA-Z0-9_$]*/;
 
diff --git a/src/parse/state/tag.ts b/src/parse/state/tag.ts
index 4fbc9c9767..c492d99bc1 100644
--- a/src/parse/state/tag.ts
+++ b/src/parse/state/tag.ts
@@ -2,9 +2,9 @@ import readExpression from '../read/expression.ts';
 import readScript from '../read/script.ts';
 import readStyle from '../read/style.ts';
 import { readEventHandlerDirective, readBindingDirective, readTransitionDirective } from '../read/directives.ts';
-import { trimStart, trimEnd } from '../../utils/trim.js';
+import { trimStart, trimEnd } from '../../utils/trim.ts';
 import { decodeCharacterReferences } from '../utils/html.ts';
-import isVoidElementName from '../../utils/isVoidElementName.js';
+import isVoidElementName from '../../utils/isVoidElementName.ts';
 
 const validTagName = /^\!?[a-zA-Z]{1,}:?[a-zA-Z0-9\-]*/;
 const invalidUnquotedAttributeCharacters = /[\s"'=<>\/`]/;
diff --git a/src/utils/CodeBuilder.js b/src/utils/CodeBuilder.ts
similarity index 100%
rename from src/utils/CodeBuilder.js
rename to src/utils/CodeBuilder.ts
diff --git a/src/utils/__test__.js b/src/utils/__test__.ts
similarity index 98%
rename from src/utils/__test__.js
rename to src/utils/__test__.ts
index 54e173d5f9..d97990aec3 100644
--- a/src/utils/__test__.js
+++ b/src/utils/__test__.ts
@@ -1,6 +1,6 @@
 import * as assert from 'assert';
 import deindent from './deindent.js';
-import CodeBuilder from './CodeBuilder.js';
+import CodeBuilder from './CodeBuilder.ts';
 
 describe( 'deindent', () => {
 	it( 'deindents a simple string', () => {
diff --git a/src/utils/annotateWithScopes.js b/src/utils/annotateWithScopes.ts
similarity index 100%
rename from src/utils/annotateWithScopes.js
rename to src/utils/annotateWithScopes.ts
diff --git a/src/utils/flattenReference.js b/src/utils/flattenReference.ts
similarity index 100%
rename from src/utils/flattenReference.js
rename to src/utils/flattenReference.ts
diff --git a/src/utils/getCodeFrame.js b/src/utils/getCodeFrame.ts
similarity index 100%
rename from src/utils/getCodeFrame.js
rename to src/utils/getCodeFrame.ts
diff --git a/src/utils/globalWhitelist.js b/src/utils/globalWhitelist.ts
similarity index 100%
rename from src/utils/globalWhitelist.js
rename to src/utils/globalWhitelist.ts
diff --git a/src/utils/isReference.js b/src/utils/isReference.ts
similarity index 100%
rename from src/utils/isReference.js
rename to src/utils/isReference.ts
diff --git a/src/utils/isVoidElementName.js b/src/utils/isVoidElementName.ts
similarity index 100%
rename from src/utils/isVoidElementName.js
rename to src/utils/isVoidElementName.ts
diff --git a/src/utils/namespaces.js b/src/utils/namespaces.ts
similarity index 100%
rename from src/utils/namespaces.js
rename to src/utils/namespaces.ts
diff --git a/src/utils/patterns.js b/src/utils/patterns.ts
similarity index 100%
rename from src/utils/patterns.js
rename to src/utils/patterns.ts
diff --git a/src/utils/removeNode.js b/src/utils/removeNode.ts
similarity index 100%
rename from src/utils/removeNode.js
rename to src/utils/removeNode.ts
diff --git a/src/utils/reservedNames.js b/src/utils/reservedNames.ts
similarity index 100%
rename from src/utils/reservedNames.js
rename to src/utils/reservedNames.ts
diff --git a/src/utils/toSource.js b/src/utils/toSource.ts
similarity index 100%
rename from src/utils/toSource.js
rename to src/utils/toSource.ts
diff --git a/src/utils/trim.js b/src/utils/trim.ts
similarity index 85%
rename from src/utils/trim.js
rename to src/utils/trim.ts
index c64d7b26a2..b2330bc5d0 100644
--- a/src/utils/trim.js
+++ b/src/utils/trim.ts
@@ -1,4 +1,4 @@
-import { whitespace } from './patterns.js';
+import { whitespace } from './patterns.ts';
 
 export function trimStart ( str ) {
 	let i = 0;
diff --git a/src/validate/html/index.js b/src/validate/html/index.ts
similarity index 91%
rename from src/validate/html/index.js
rename to src/validate/html/index.ts
index 13b627f73a..fe5edbc489 100644
--- a/src/validate/html/index.js
+++ b/src/validate/html/index.ts
@@ -1,6 +1,6 @@
-import * as namespaces from '../../utils/namespaces.js';
-import validateElement from './validateElement.js';
-import validateWindow from './validateWindow.js';
+import * as namespaces from '../../utils/namespaces.ts';
+import validateElement from './validateElement.ts';
+import validateWindow from './validateWindow.ts';
 
 const svg = /^(?:altGlyph|altGlyphDef|altGlyphItem|animate|animateColor|animateMotion|animateTransform|circle|clipPath|color-profile|cursor|defs|desc|discard|ellipse|feBlend|feColorMatrix|feComponentTransfer|feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|feDistantLight|feDropShadow|feFlood|feFuncA|feFuncB|feFuncG|feFuncR|feGaussianBlur|feImage|feMerge|feMergeNode|feMorphology|feOffset|fePointLight|feSpecularLighting|feSpotLight|feTile|feTurbulence|filter|font|font-face|font-face-format|font-face-name|font-face-src|font-face-uri|foreignObject|g|glyph|glyphRef|hatch|hatchpath|hkern|image|line|linearGradient|marker|mask|mesh|meshgradient|meshpatch|meshrow|metadata|missing-glyph|mpath|path|pattern|polygon|polyline|radialGradient|rect|set|solidcolor|stop|switch|symbol|text|textPath|title|tref|tspan|unknown|use|view|vkern)$/;
 
diff --git a/src/validate/html/validateElement.js b/src/validate/html/validateElement.ts
similarity index 98%
rename from src/validate/html/validateElement.js
rename to src/validate/html/validateElement.ts
index 74034ceb08..8d902b1af3 100644
--- a/src/validate/html/validateElement.js
+++ b/src/validate/html/validateElement.ts
@@ -1,4 +1,4 @@
-import validateEventHandler from './validateEventHandler.js';
+import validateEventHandler from './validateEventHandler.ts';
 
 export default function validateElement ( validator, node ) {
 	const isComponent = node.name === ':Self' || validator.components.has( node.name );
diff --git a/src/validate/html/validateEventHandler.js b/src/validate/html/validateEventHandler.ts
similarity index 90%
rename from src/validate/html/validateEventHandler.js
rename to src/validate/html/validateEventHandler.ts
index 3c0f1f288d..17bcca3c20 100644
--- a/src/validate/html/validateEventHandler.js
+++ b/src/validate/html/validateEventHandler.ts
@@ -1,5 +1,5 @@
-import flattenReference from '../../utils/flattenReference.js';
-import list from '../utils/list.js';
+import flattenReference from '../../utils/flattenReference.ts';
+import list from '../utils/list.ts';
 
 const validBuiltins = new Set([
 	'set',
diff --git a/src/validate/html/validateWindow.js b/src/validate/html/validateWindow.ts
similarity index 85%
rename from src/validate/html/validateWindow.js
rename to src/validate/html/validateWindow.ts
index e719691622..c9fd9996ad 100644
--- a/src/validate/html/validateWindow.js
+++ b/src/validate/html/validateWindow.ts
@@ -1,7 +1,7 @@
-import flattenReference from '../../utils/flattenReference.js';
-import fuzzymatch from '../utils/fuzzymatch.js';
-import list from '../utils/list.js';
-import validateEventHandler from './validateEventHandler.js';
+import flattenReference from '../../utils/flattenReference.ts';
+import fuzzymatch from '../utils/fuzzymatch.ts';
+import list from '../utils/list.ts';
+import validateEventHandler from './validateEventHandler.ts';
 
 const validBindings = [
 	'innerWidth',
diff --git a/src/validate/index.js b/src/validate/index.ts
similarity index 92%
rename from src/validate/index.js
rename to src/validate/index.ts
index 8991803ba5..5e219e644e 100644
--- a/src/validate/index.js
+++ b/src/validate/index.ts
@@ -1,7 +1,7 @@
-import validateJs from './js/index.js';
-import validateHtml from './html/index.js';
+import validateJs from './js/index.ts';
+import validateHtml from './html/index.ts';
 import { getLocator } from 'locate-character';
-import getCodeFrame from '../utils/getCodeFrame.js';
+import getCodeFrame from '../utils/getCodeFrame.ts';
 
 export default function validate ( parsed, source, { onerror, onwarn, name, filename } ) {
 	const locator = getLocator( source );
diff --git a/src/validate/js/index.js b/src/validate/js/index.ts
similarity index 89%
rename from src/validate/js/index.js
rename to src/validate/js/index.ts
index 5b101502ef..fa0bde7d97 100644
--- a/src/validate/js/index.js
+++ b/src/validate/js/index.ts
@@ -1,8 +1,8 @@
-import propValidators from './propValidators/index.js';
-import fuzzymatch from '../utils/fuzzymatch.js';
-import checkForDupes from './utils/checkForDupes.js';
-import checkForComputedKeys from './utils/checkForComputedKeys.js';
-import namespaces from '../../utils/namespaces.js';
+import propValidators from './propValidators/index.ts';
+import fuzzymatch from '../utils/fuzzymatch.ts';
+import checkForDupes from './utils/checkForDupes.ts';
+import checkForComputedKeys from './utils/checkForComputedKeys.ts';
+import namespaces from '../../utils/namespaces.ts';
 
 const validPropList = Object.keys( propValidators );
 
diff --git a/src/validate/js/propValidators/components.js b/src/validate/js/propValidators/components.ts
similarity index 92%
rename from src/validate/js/propValidators/components.js
rename to src/validate/js/propValidators/components.ts
index 06bb504ecf..4a7ecc5de5 100644
--- a/src/validate/js/propValidators/components.js
+++ b/src/validate/js/propValidators/components.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes.js';
-import checkForComputedKeys from '../utils/checkForComputedKeys.js';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 export default function components ( validator, prop ) {
 	if ( prop.value.type !== 'ObjectExpression' ) {
diff --git a/src/validate/js/propValidators/computed.js b/src/validate/js/propValidators/computed.ts
similarity index 95%
rename from src/validate/js/propValidators/computed.js
rename to src/validate/js/propValidators/computed.ts
index 16f8e36190..e02f7e5006 100644
--- a/src/validate/js/propValidators/computed.js
+++ b/src/validate/js/propValidators/computed.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes.js';
-import checkForComputedKeys from '../utils/checkForComputedKeys.js';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 const isFunctionExpression = new Set( [ 'FunctionExpression', 'ArrowFunctionExpression' ] );
 
diff --git a/src/validate/js/propValidators/data.js b/src/validate/js/propValidators/data.ts
similarity index 100%
rename from src/validate/js/propValidators/data.js
rename to src/validate/js/propValidators/data.ts
diff --git a/src/validate/js/propValidators/events.js b/src/validate/js/propValidators/events.ts
similarity index 86%
rename from src/validate/js/propValidators/events.js
rename to src/validate/js/propValidators/events.ts
index 437b259132..efcef44e17 100644
--- a/src/validate/js/propValidators/events.js
+++ b/src/validate/js/propValidators/events.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes.js';
-import checkForComputedKeys from '../utils/checkForComputedKeys.js';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 export default function events ( validator, prop ) {
 	if ( prop.value.type !== 'ObjectExpression' ) {
diff --git a/src/validate/js/propValidators/helpers.js b/src/validate/js/propValidators/helpers.ts
similarity index 96%
rename from src/validate/js/propValidators/helpers.js
rename to src/validate/js/propValidators/helpers.ts
index 7e27e31134..070ba12acb 100644
--- a/src/validate/js/propValidators/helpers.js
+++ b/src/validate/js/propValidators/helpers.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes.js';
-import checkForComputedKeys from '../utils/checkForComputedKeys.js';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 import { walk } from 'estree-walker';
 
 export default function helpers ( validator, prop ) {
diff --git a/src/validate/js/propValidators/index.js b/src/validate/js/propValidators/index.js
deleted file mode 100644
index 36dea150fb..0000000000
--- a/src/validate/js/propValidators/index.js
+++ /dev/null
@@ -1,27 +0,0 @@
-import data from './data.js';
-import computed from './computed.js';
-import oncreate from './oncreate.js';
-import ondestroy from './ondestroy.js';
-import onrender from './onrender.js';
-import onteardown from './onteardown.js';
-import helpers from './helpers.js';
-import methods from './methods.js';
-import components from './components.js';
-import events from './events.js';
-import namespace from './namespace.js';
-import transitions from './transitions.js';
-
-export default {
-	data,
-	computed,
-	oncreate,
-	ondestroy,
-	onrender,
-	onteardown,
-	helpers,
-	methods,
-	components,
-	events,
-	namespace,
-	transitions
-};
diff --git a/src/validate/js/propValidators/index.ts b/src/validate/js/propValidators/index.ts
new file mode 100644
index 0000000000..ffbf9306c8
--- /dev/null
+++ b/src/validate/js/propValidators/index.ts
@@ -0,0 +1,27 @@
+import data from './data.ts';
+import computed from './computed.ts';
+import oncreate from './oncreate.ts';
+import ondestroy from './ondestroy.ts';
+import onrender from './onrender.ts';
+import onteardown from './onteardown.ts';
+import helpers from './helpers.ts';
+import methods from './methods.ts';
+import components from './components.ts';
+import events from './events.ts';
+import namespace from './namespace.ts';
+import transitions from './transitions.ts';
+
+export default {
+	data,
+	computed,
+	oncreate,
+	ondestroy,
+	onrender,
+	onteardown,
+	helpers,
+	methods,
+	components,
+	events,
+	namespace,
+	transitions
+};
diff --git a/src/validate/js/propValidators/methods.js b/src/validate/js/propValidators/methods.ts
similarity index 83%
rename from src/validate/js/propValidators/methods.js
rename to src/validate/js/propValidators/methods.ts
index 0bddc3d184..0de3fa8fad 100644
--- a/src/validate/js/propValidators/methods.js
+++ b/src/validate/js/propValidators/methods.ts
@@ -1,7 +1,7 @@
-import checkForAccessors from '../utils/checkForAccessors.js';
-import checkForDupes from '../utils/checkForDupes.js';
-import checkForComputedKeys from '../utils/checkForComputedKeys.js';
-import usesThisOrArguments from '../utils/usesThisOrArguments.js';
+import checkForAccessors from '../utils/checkForAccessors.ts';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
+import usesThisOrArguments from '../utils/usesThisOrArguments.ts';
 
 const builtin = new Set( [ 'set', 'get', 'on', 'fire', 'observe', 'destroy' ] );
 
diff --git a/src/validate/js/propValidators/namespace.js b/src/validate/js/propValidators/namespace.ts
similarity index 84%
rename from src/validate/js/propValidators/namespace.js
rename to src/validate/js/propValidators/namespace.ts
index be011c45d7..b96e2361b5 100644
--- a/src/validate/js/propValidators/namespace.js
+++ b/src/validate/js/propValidators/namespace.ts
@@ -1,5 +1,5 @@
-import * as namespaces from '../../../utils/namespaces.js';
-import fuzzymatch from '../../utils/fuzzymatch.js';
+import * as namespaces from '../../../utils/namespaces.ts';
+import fuzzymatch from '../../utils/fuzzymatch.ts';
 
 const valid = new Set( namespaces.validNamespaces );
 
diff --git a/src/validate/js/propValidators/oncreate.js b/src/validate/js/propValidators/oncreate.ts
similarity index 81%
rename from src/validate/js/propValidators/oncreate.js
rename to src/validate/js/propValidators/oncreate.ts
index 3d863ec726..55ee524b30 100644
--- a/src/validate/js/propValidators/oncreate.js
+++ b/src/validate/js/propValidators/oncreate.ts
@@ -1,4 +1,4 @@
-import usesThisOrArguments from '../utils/usesThisOrArguments.js';
+import usesThisOrArguments from '../utils/usesThisOrArguments.ts';
 
 export default function oncreate ( validator, prop ) {
 	if ( prop.value.type === 'ArrowFunctionExpression' ) {
diff --git a/src/validate/js/propValidators/ondestroy.js b/src/validate/js/propValidators/ondestroy.ts
similarity index 81%
rename from src/validate/js/propValidators/ondestroy.js
rename to src/validate/js/propValidators/ondestroy.ts
index 3471034178..3dae006f1b 100644
--- a/src/validate/js/propValidators/ondestroy.js
+++ b/src/validate/js/propValidators/ondestroy.ts
@@ -1,4 +1,4 @@
-import usesThisOrArguments from '../utils/usesThisOrArguments.js';
+import usesThisOrArguments from '../utils/usesThisOrArguments.ts';
 
 export default function ondestroy ( validator, prop ) {
 	if ( prop.value.type === 'ArrowFunctionExpression' ) {
diff --git a/src/validate/js/propValidators/onrender.js b/src/validate/js/propValidators/onrender.ts
similarity index 85%
rename from src/validate/js/propValidators/onrender.js
rename to src/validate/js/propValidators/onrender.ts
index 4f0cad4fbb..49530326e0 100644
--- a/src/validate/js/propValidators/onrender.js
+++ b/src/validate/js/propValidators/onrender.ts
@@ -1,4 +1,4 @@
-import oncreate from './oncreate.js';
+import oncreate from './oncreate.ts';
 
 export default function onrender ( validator, prop ) {
 	validator.warn( `'onrender' has been deprecated in favour of 'oncreate', and will cause an error in Svelte 2.x`, prop.start );
diff --git a/src/validate/js/propValidators/onteardown.js b/src/validate/js/propValidators/onteardown.ts
similarity index 84%
rename from src/validate/js/propValidators/onteardown.js
rename to src/validate/js/propValidators/onteardown.ts
index c1038d4365..ec7cfb9bc3 100644
--- a/src/validate/js/propValidators/onteardown.js
+++ b/src/validate/js/propValidators/onteardown.ts
@@ -1,4 +1,4 @@
-import ondestroy from './ondestroy.js';
+import ondestroy from './ondestroy.ts';
 
 export default function onteardown ( validator, prop ) {
 	validator.warn( `'onteardown' has been deprecated in favour of 'ondestroy', and will cause an error in Svelte 2.x`, prop.start );
diff --git a/src/validate/js/propValidators/transitions.js b/src/validate/js/propValidators/transitions.ts
similarity index 89%
rename from src/validate/js/propValidators/transitions.js
rename to src/validate/js/propValidators/transitions.ts
index a7580cc92a..5287a1f803 100644
--- a/src/validate/js/propValidators/transitions.js
+++ b/src/validate/js/propValidators/transitions.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes.js';
-import checkForComputedKeys from '../utils/checkForComputedKeys.js';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 export default function transitions ( validator, prop ) {
 	if ( prop.value.type !== 'ObjectExpression' ) {
diff --git a/src/validate/js/utils/checkForAccessors.js b/src/validate/js/utils/checkForAccessors.ts
similarity index 100%
rename from src/validate/js/utils/checkForAccessors.js
rename to src/validate/js/utils/checkForAccessors.ts
diff --git a/src/validate/js/utils/checkForComputedKeys.js b/src/validate/js/utils/checkForComputedKeys.ts
similarity index 100%
rename from src/validate/js/utils/checkForComputedKeys.js
rename to src/validate/js/utils/checkForComputedKeys.ts
diff --git a/src/validate/js/utils/checkForDupes.js b/src/validate/js/utils/checkForDupes.ts
similarity index 100%
rename from src/validate/js/utils/checkForDupes.js
rename to src/validate/js/utils/checkForDupes.ts
diff --git a/src/validate/js/utils/usesThisOrArguments.js b/src/validate/js/utils/usesThisOrArguments.ts
similarity index 89%
rename from src/validate/js/utils/usesThisOrArguments.js
rename to src/validate/js/utils/usesThisOrArguments.ts
index 40fffc0a5c..dfc2044c6d 100644
--- a/src/validate/js/utils/usesThisOrArguments.js
+++ b/src/validate/js/utils/usesThisOrArguments.ts
@@ -1,5 +1,5 @@
 import { walk } from 'estree-walker';
-import isReference from '../../../utils/isReference.js';
+import isReference from '../../../utils/isReference.ts';
 
 export default function usesThisOrArguments ( node ) {
 	let result = false;
diff --git a/src/validate/utils/FuzzySet.js b/src/validate/utils/FuzzySet.ts
similarity index 100%
rename from src/validate/utils/FuzzySet.js
rename to src/validate/utils/FuzzySet.ts
diff --git a/src/validate/utils/fuzzymatch.js b/src/validate/utils/fuzzymatch.ts
similarity index 84%
rename from src/validate/utils/fuzzymatch.js
rename to src/validate/utils/fuzzymatch.ts
index 7eabd79090..62bc770f87 100644
--- a/src/validate/utils/fuzzymatch.js
+++ b/src/validate/utils/fuzzymatch.ts
@@ -1,4 +1,4 @@
-import FuzzySet from './FuzzySet.js';
+import FuzzySet from './FuzzySet.ts';
 
 export default function fuzzymatch ( name, names ) {
 	const set = new FuzzySet( names );
diff --git a/src/validate/utils/list.js b/src/validate/utils/list.ts
similarity index 100%
rename from src/validate/utils/list.js
rename to src/validate/utils/list.ts