Syntax error of Worker code in IE11

[wyleung]

Thank you for the great work on this VectorGrid!

It works fine in Webkit based browsers and Edge. However, when I was testing it in IE 11, it was crashing on: https://github.com/Leaflet/Leaflet.VectorGrid/blob/master/src/Leaflet.VectorGrid.Slicer.js#L33

I'd not take any actions yet to debug / rewrite this part of code. Is anyone seeing the same issue ?

[IvanSanchez]

We'll need more information. What is the exact parse error?

By using an instance of Chrome (or Chromium) and using the "sources" tab of the dev console, it's easy to see the code that the worker is running. If you copy-paste that code into a standalone file and load it with IE11, does a (better) error appear?

[wyleung]

Setup:

Leaflet v1.0.2
Leaflet.VectorGrid: https://leaflet.github.io/Leaflet.VectorGrid/dist/Leaflet.VectorGrid.bundled.js
Internet Explorer: 11.0.9600.18537

Screenshot:

[IvanSanchez]

Yeah, it's failing to parse the code inside the blob:, but it's not displaying any good information on which line is failing. This will need a bit of extra investigation. :-(

[wyleung]

@IvanSanchez Too bad :( I can spend some time on this issue today..

[dosstx]

I had this same issue at the office, but I can't seem to replicate at home. I think I solved it by adding some polyfills to the head of my HTML like so:

<script src="fetch-ie8/fetch.js"></script>
<script src="es6-promise/dist/es6-promise.js"></script> 

Does that solve your issue? Make sure you grab the latest versions of those polyfills because I think there was some bad code in earlier versions.

You can try my demo and see if you have any issues with the web workers: https://goo.gl/GeavZS

[jklongi]

I am also getting this in IE all version except Edge. Very hard to debugg since its inside the blob. Any news / suggestions on this? The solution by dosstx did not work.

[dosstx]

@jklongi Did you add the function to your code to call the polyfills?

ES6Promise.polyfill();

I'm using IE11 and it works for me....

[perliedman]

I don't think any of the maintainers have IE as a priority, so this would be a good time to step up and submit a PR! We would really appreciate help with this.

[jklongi]

@dosstx Yes I did but it doesn't help. I cant get my code or nor even your example to work. Just facing the same error as @wyleung . I am using browserstack and couple real windows machines to get IE 11 & 10 but not any of them work.

I looked into it and I think the function that gives the worker code __$strToBlobUri is returning the blob in every other browser like so: "blob:http://localhost:8000/fe350922-c073-4d79-af88-cf5c194ccfac" but in IE it returns the blob input as a string but it has been cut off like so:

"data:text/plain; charset=us-ascii,'use strict';

var simplify_1 = simplify$1;

// calculate simplification data using optimized Douglas-Peucker algorithm

function simplify$1(points, tolerance) {

    var sqTolerance = tolerance * tolerance,
        len = points.length,
        first = 0,
        last = len - 1,
        stack = [],
        i, maxSqDist, sqDist, index;

    // always retain the endpoints (1 is the max value)
    points[first][2] = 1;
    points[last][2] = 1;

    // avoid recursion by using a stack
    while (last) {

        maxSqDist = 0;

        for (i = first + 1; i < last; i++) {
            sqDist = getSqSegDist(points[i], points[first], points[last]);

            if (sqDist > maxSqDist) {
                index = i;
                maxSqDist = sqDist;
            }
        }

        if (maxSqDist > sqTolerance) {
            points[index][2] = maxSqDist; // save the point importance in squared pixels as a z coordinate
            stack.push(first);
            stack.push(index);
     "

However the stuff inside that function might be beyond my skill to debugg..

[jklongi]

I was actually able to (kind of) solve this by using the workerCode from version 1.1.0 and calling the worker with this._worker = new Worker(window.URL.createObjectURL(new Blob([workerCode])));
So there is something going on with the forming of new worker code through that __$strToBlobUri function.

[msully]

Thanks @IvanSanchez for creating a great Leaflet Plugin.
I have the same issue with IE 11 as reported.

Any recommendations for a fix?

[msully]

@IvanSanchez this may be helpful in understanding the IE 11 issue.
A web application that uses the Web Worker blob method may not function in Internet Explorer 11
https://support.microsoft.com/en-us/help/3023851

[IvanSanchez]

@msully Hhhhmmm, not very helpful, albeit interesting.

Maybe loading the VectorGrid file with a <script src=... crossorigin='anonymous'> will make something happen?

[msully]

@IvanSanchez unfortunately loading the VectorGrid file <script src=... crossorigin='anonymous'> had no effect.

Two steps to resolve the IE11 issue:

1. I remove the variable "workerCode" as a blob URL and moved the worker code into an external file lccWebWorker.js.
   Then referenced it as var lccworkerCode = './js/lccWebWorker.js';

initialize: function(t, e) {
        L.VectorGrid.prototype.initialize.call(this, e);
        var e = {};
        var lccworkerCode = './js/lccWebWorker.js';
        for (var r in this.options) "rendererFactory" !== r && "vectorTileLayerStyles" !== r && "function" != typeof this.options[r] && (e[r] = this.options[r]);
        this._worker = new Worker(lccworkerCode), this._worker.postMessage(["slice", t, e])
    },

2. Added IE 11 Promise support: http://stackoverflow.com/questions/36016327/how-to-make-promises-work-in-ie11

A working example : Grass cutting map

[Harvinator]

Thanks @msully

For me I changed one line in the L.VectorGrid.Slicer initialize function

From...
this._worker = new Worker(workerCode);
To...
this._worker = new Worker(options.workerCode || workerCode);

Then when creating my layer

L.vectorGrid.slicer(geoJson, {
    workerCode: '/path/to/Leaflet.VectorGrid/WebWorker.js',
    [...]
}).addTo(map);

The code that goes in WebWorker came from var workerCode = __$strToBlobUri("...HERE..."); in the distributed source (just had to replace \n with new line and \" with ")