fix for usage of baseURI which doesn't work in IE11

runtime/src/app/baseuri_helper.ts

@@ -0,0 +1,10 @@
+export function get_base_uri(window_document) {
+	let baseURI = window_document.baseURI;
+
+	if (!baseURI) {
+		const baseTags = window_document.getElementsByTagName('base');
+		baseURI = baseTags.length ? baseTags[0].href : window_document.URL;
+	}
+
+	return baseURI;
+}

runtime/src/app/goto/index.ts

@@ -1,10 +1,11 @@
 import { cid, history, navigate, select_target } from '../router';
+import { get_base_uri } from '../baseuri_helper';
 
 export default function goto(
 		href: string,
 		opts: { noscroll?: boolean, replaceState?: boolean } = { noscroll: false, replaceState: false }): Promise<void> {
 
-	const target = select_target(new URL(href, document.baseURI));
+	const target = select_target(new URL(href, get_base_uri(document)));
 
 	if (target) {
 		history[opts.replaceState ? 'replaceState' : 'pushState']({ id: cid }, '', href);

runtime/src/app/prefetch/index.ts

@@ -2,6 +2,7 @@ import { hydrate_target } from '../app';
 import { select_target } from '../router';
 import find_anchor from '../router/find_anchor';
 import { HydratedTarget, Target } from '../types';
+import { get_base_uri } from '../baseuri_helper';
 
 let prefetching: {
 	href: string;
@@ -16,7 +17,7 @@ export function start() {
 }
 
 export default function prefetch(href: string) {
-	const target = select_target(new URL(href, document.baseURI));
+	const target = select_target(new URL(href, get_base_uri(document)));
 
 	if (target) {
 		if (!prefetching || href !== prefetching.href) {

src/core/create_compilers/RollupCompiler.ts

@@ -25,7 +25,14 @@ const inject_styles = `
 export default function(files) {
 	return Promise.all(files.map(function(file) { return new Promise(function(fulfil, reject) {
 		var href = new URL(file, import.meta.url);
-		var relative = ('' + href).substring(document.baseURI.length);
+		var baseURI = document.baseURI;
+
+		if (!baseURI) {
+			var baseTags = document.getElementsByTagName('base');
+			baseURI = baseTags.length ? baseTags[0].href : document.URL;
+		}
+
+		var relative = ('' + href).substring(baseURI.length);
 		var link = document.querySelector('link[rel=stylesheet][href="' + relative + '"]')
 			|| document.querySelector('link[rel=stylesheet][href="' + href + '"]');
 		if (!link) {

test/unit/baseuri_helper/test.ts

@@ -0,0 +1,42 @@
+import * as assert from 'assert';
+import { get_base_uri } from '../../../runtime/src/app/baseuri_helper';
+
+describe('get_base_uri', () => {
+	it('document.baseURI exists', () => {
+		const baseUri = 'https://baseuri.example.com';
+		const document = {
+			baseURI: baseUri
+		};
+		assert.strictEqual(get_base_uri(document), baseUri);
+	});
+
+	it('document.baseURI does not exist, with <base /> tag', () => {
+		const baseUri = 'https://bytag.example.com';
+		const document = {
+			getElementsByTagName: () => [
+				{ href: baseUri }
+			]
+		};
+		assert.strictEqual(get_base_uri(document), baseUri);
+	});
+
+	it('document.baseURI does not exist, with multiple <base /> tag', () => {
+		const baseUri = 'https://fromtag.example.com';
+		const document = {
+			getElementsByTagName: () => [
+				{ href: baseUri },
+				{ href: 'https://ignoreme.example.com' }
+			]
+		};
+		assert.strictEqual(get_base_uri(document), baseUri);
+	});
+
+	it('document.baseURI does not exist, without <base /> tag', () => {
+		const baseUri = 'https://byurl.example.com';
+		const document = {
+			getElementsByTagName: () => [],
+			URL: baseUri
+		};
+		assert.strictEqual(get_base_uri(document), baseUri);
+	});
+});