Can not open certain maps with OpenLayers / IE11

[offtherailz]

Description

Maps with tileXYZ layers that contain subdomains can not be opened in IE11

In case of Bug (otherwise remove this paragraph)

Browser Affected
(use this site: https://www.whatsmybrowser.org/ for non expert users)

• Internet Explorer
• Chrome
• Firefox
• Safari

Browser Version Affected

• 10 and 11

Steps to reproduce

• Use Internet Explorer 11 to open this map

Expected Result

• The map can open

Current Result

• The map remain in loading

Other useful information (optional):

It seems to be due to usage of of (2 times)

MapStore2/web/client/components/map/openlayers/plugins/TileProviderLayer.js

Line 35 in a1ff7d2

for (let c of opt.subdomains) {

not supported in IE 11

something like

if (opt.subdomains) {
        opt.subdomains.map( c => urls.push(template(url.replace("{s}", c), opt)));
    } else {
        ['a', 'b', 'c'].map( c => urls.push(template(url.replace("{s}", c), opt)));
    }

make the application work in IE11.

Check my temp work at:
https://github.com/offtherailz/MapStore2/tree/fix_%232685