Useful or not, from you.
svelte Svelte applications fail to load in IE 11. Similar loading issue with the main site svelte.dev

image

Digging closer the error is on this line:

const identity = x => x;

I suspect I need a polyfill but there doesn't seem to be an appropriate one. Svelte version: 3.0.0

The home page: https://svelte.dev/ gives this error: (as of 30/04/2019)

image

IE version:

image

That's a useful answer
Without any help

Sorry for appending to a closed thread, but since this is the first hit that comes up when looking for IE11 and Sapper issues I thought I should post here. Sapper uses document.baseURI in goto and prefetch which isn't supported in IE11 and doesn't appear to be polyfilled by Babel or polyfill.io.

TypeError: Invalid scheme

is a hint that this might be biting you.

I found this patch which works for me when added to template.html along with the polyfill.io polyfills mentioned in Usage of shimport makes legacy support prohibitively challenging

source: https://github.com/webcomponents/webcomponents-platform/issues/2

if ('baseURI' in Node.prototype === false) {
  Object.defineProperty(Node.prototype, 'baseURI', {
    get: function() {
      var base = (this.ownerDocument || this).querySelector('base');
      return (base || window.location).href;
    },
    configurable: true,
    enumerable: true
  });
}

Maybe a polyfill for this could be added to --legacy builds automatically in a future release?