store regexp as variable instead of defining it inline

src/compiler/preprocess/index.ts

@@ -13,8 +13,10 @@ interface SourceUpdate {
 	dependencies?: string[];
 }
 
+const regex_filepath_separator = /[/\\]/;
+
 function get_file_basename(filename: string) {
-	return filename.split(/[/\\]/).pop();
+	return filename.split(regex_filepath_separator).pop();
 }
 
 /**
@@ -120,20 +122,27 @@ function processed_tag_to_code(
 	return tag_open_code.concat(content_code).concat(tag_close_code);
 }
 
+const regex_whitespace = /\s+/;
+const regex_unquoted_value = /^['"](.*)['"]$/;
+
 function parse_tag_attributes(str: string) {
 	// note: won't work with attribute values containing spaces.
 	return str
-		.split(/\s+/)
+		.split(regex_whitespace)
 		.filter(Boolean)
 		.reduce((attrs, attr) => {
 			const i = attr.indexOf('=');
 			const [key, value] = i > 0 ? [attr.slice(0, i), attr.slice(i + 1)] : [attr];
-			const [, unquoted] = (value && value.match(/^['"](.*)['"]$/)) || [];
+			const [, unquoted] = (value && value.match(regex_unquoted_value)) || [];
 
 			return { ...attrs, [key]: unquoted ?? value ?? true };
 		}, {});
 }
 
+
+const regex_style_tags = /<!--[^]*?-->|<style(\s[^]*?)?(?:>([^]*?)<\/style>|\/>)/gi;
+const regex_script_tags = /<!--[^]*?-->|<script(\s[^]*?)?(?:>([^]*?)<\/script>|\/>)/gi;
+
 /**
  * Calculate the updates required to process all instances of the specified tag.
  */
@@ -143,10 +152,7 @@ async function process_tag(
 	source: Source
 ): Promise<SourceUpdate> {
 	const { filename, source: markup } = source;
-	const tag_regex =
-		tag_name === 'style'
-			? /<!--[^]*?-->|<style(\s[^]*?)?(?:>([^]*?)<\/style>|\/>)/gi
-			: /<!--[^]*?-->|<script(\s[^]*?)?(?:>([^]*?)<\/script>|\/>)/gi;
+	const tag_regex = tag_name === 'style' ? regex_style_tags : regex_script_tags;
 
 	const dependencies: string[] = [];
 
@@ -190,7 +196,7 @@ async function process_markup(process: MarkupPreprocessor, source: Source) {
 			string: processed.code,
 			map: processed.map
 				? // TODO: can we use decode_sourcemap?
-				  typeof processed.map === 'string'
+				typeof processed.map === 'string'
 					? JSON.parse(processed.map)
 					: processed.map
 				: undefined,

src/compiler/utils/extract_svelte_ignore.ts

@@ -3,9 +3,11 @@ import { flatten } from './flatten';
 
 const pattern = /^\s*svelte-ignore\s+([\s\S]+)\s*$/m;
 
+const regex_no_whitespace_character = /[^\S]/;
+
 export function extract_svelte_ignore(text: string): string[] {
 	const match = pattern.exec(text);
-	return match ? match[1].split(/[^\S]/).map(x => x.trim()).filter(Boolean) : [];
+	return match ? match[1].split(regex_no_whitespace_character).map(x => x.trim()).filter(Boolean) : [];
 }
 
 export function extract_svelte_ignore_from_comments<Node extends { leadingComments?: Array<{value: string}> }>(node: Node): string[] {

src/compiler/utils/get_code_frame.ts

@@ -1,5 +1,7 @@
+const regex_tabs = /^\t+/;
+
 function tabs_to_spaces(str: string) {
-	return str.replace(/^\t+/, match => match.split('\t').join('  '));
+	return str.replace(regex_tabs, match => match.split('\t').join('  '));
 }
 
 export default function get_code_frame(

src/compiler/utils/mapped_code.ts

@@ -182,6 +182,8 @@ export class MappedCode {
 		return new MappedCode(string, map);
 	}
 
+	private static regex_line_token = /([^\d\w\s]|\s+)/g;
+
 	static from_source({ source, file_basename, get_location }: Source): MappedCode {
 		let offset: SourceLocation = get_location(0);
 
@@ -195,7 +197,7 @@ export class MappedCode {
 		const line_list = source.split('\n');
 		for (let line = 0; line < line_list.length; line++) {
 			map.mappings.push([]);
-			const token_list = line_list[line].split(/([^\d\w\s]|\s+)/g);
+			const token_list = line_list[line].split(this.regex_line_token);
 			for (let token = 0, column = 0; token < token_list.length; token++) {
 				if (token_list[token] == '') continue;
 				map.mappings[line].push([column, 0, offset.line + line, column]);
@@ -245,7 +247,7 @@ export function combine_sourcemaps(
 	if (!map.file) delete map.file; // skip optional field `file`
 
 	// When source maps are combined and the leading map is empty, sources is not set.
-	// Add the filename to the empty array in this case. 
+	// Add the filename to the empty array in this case.
 	// Further improvements to remapping may help address this as well https://github.com/ampproject/remapping/issues/116
 	if (!map.sources.length) map.sources = [filename];
 
@@ -289,6 +291,8 @@ export function apply_preprocessor_sourcemap(filename: string, svelte_map: Sourc
 	return result_map as SourceMap;
 }
 
+const regex_data_uri = /data:(?:application|text)\/json;(?:charset[:=]\S+?;)?base64,(\S*)/;
+
 // parse attached sourcemap in processed.code
 export function parse_attached_sourcemap(processed: Processed, tag_name: 'script' | 'style'): void {
 	const r_in = '[#@]\\s*sourceMappingURL\\s*=\\s*(\\S*)';
@@ -302,7 +306,7 @@ export function parse_attached_sourcemap(processed: Processed, tag_name: 'script
 	}
 	processed.code = processed.code.replace(regex, (_, match1, match2) => {
 		const map_url = (tag_name == 'script') ? (match1 || match2) : match1;
-		const map_data = (map_url.match(/data:(?:application|text)\/json;(?:charset[:=]\S+?;)?base64,(\S*)/) || [])[1];
+		const map_data = (map_url.match(regex_data_uri) || [])[1];
 		if (map_data) {
 			// sourceMappingURL is data URL
 			if (processed.map) {

src/compiler/utils/names.ts

@@ -65,10 +65,15 @@ export function is_valid(str: string): boolean {
 	return true;
 }
 
+const regex_non_standard_characters = /[^a-zA-Z0-9_]+/g;
+const regex_starts_with_underscore = /^_/;
+const regex_ends_with_underscore = /_$/;
+const regex_starts_with_number = /^[0-9]/;
+
 export function sanitize(name: string) {
 	return name
-		.replace(/[^a-zA-Z0-9_]+/g, '_')
-		.replace(/^_/, '')
-		.replace(/_$/, '')
-		.replace(/^[0-9]/, '_$&');
+		.replace(regex_non_standard_characters, '_')
+		.replace(regex_starts_with_underscore, '')
+		.replace(regex_ends_with_underscore, '')
+		.replace(regex_starts_with_number, '_$&');
 }