What would be the replacement code for this such that it works across all browsers? Unfortunately the demo page does not work in IE 11. During page load (both map-pan as map-zoom) I get the error in the debugger of IE: SCRIPT438: Object doesnt support property or method assign If you must support IE 11 then I suggest you transpile a copy just for that browser and run everything else natively. Feature name. Current browser. ES6 Trans- piler. Traceur. Babel 6 core-js .binary supported by Number().