only coerce once

src/internal/dom.js

@@ -154,7 +154,8 @@ export function claim_text(nodes, data) {
 }
 
 export function set_data(text, data) {
-	if (text.data !== '' + data) text.data = '' + data;
+	data = '' + data;
+	if (text.data !== data) text.data = data;
 }
 
 export function set_input_type(input, type) {
@@ -236,4 +237,4 @@ export function custom_event(type, detail) {
 	const e = document.createEvent('CustomEvent');
 	e.initCustomEvent(type, false, false, detail);
 	return e;
-}
+}