SCRIPT438 Error in Internet Explorer 11

Finally mystery solved.

Apparently, IE9 and above supports Array.forEach but not for NodeList, which querySelector returns. I tried Array.from() to no avail as it requires ES6 or use ES6-shim.

All I had to do was to convert from nodeList to Array, and I did by this.

Array.prototype.slice.call(document.querySelectorAll("nav a"), 0);

as appeared in question In Javascript, what is the best way to convert a NodeList to an array

if (typeof Array.prototype.forEach != 'function') {
Array.prototype.forEach = function (callback) {
    for (var i = 0; i < this.length; i++) {
        callback.apply(this, [this[i], i, this]);
    }
 };
}

if (window.NodeList && !NodeList.prototype.forEach) {
    NodeList.prototype.forEach = Array.prototype.forEach;
 }