polyfills for ie 10/11 for findIndex, and forEach on nodeLists

polyfills.js

function polyfill() {

    // allow using el.querySelectorAll(...).forEach(...) for looping through nodeLists
    if (!NodeList.prototype.forEach) {
        NodeList.prototype.forEach = Array.prototype.forEach;
    }

    // allow using [].findIndex(...) in all browsers
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex
    // https://tc39.github.io/ecma262/#sec-array.prototype.findIndex
    if (!Array.prototype.findIndex) {
        Object.defineProperty(Array.prototype,
            'findIndex',
            {
                value: function(predicate) {
                    // 1. Let O be ? ToObject(this value).
                    if (this == null) {
                        throw new TypeError('"this" is null or not defined');
                    }

                    var o = Object(this);

                    // 2. Let len be ? ToLength(? Get(O, "length")).
                    var len = o.length >>> 0;

                    // 3. If IsCallable(predicate) is false, throw a TypeError exception.
                    if (typeof predicate !== 'function') {
                        throw new TypeError('predicate must be a function');
                    }

                    // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
                    var thisArg = arguments[1];

                    // 5. Let k be 0.
                    var k = 0;

                    // 6. Repeat, while k < len
                    while (k < len) {
                        // a. Let Pk be ! ToString(k).
                        // b. Let kValue be ? Get(O, Pk).
                        // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
                        // d. If testResult is true, return k.
                        var kValue = o[k];
                        if (predicate.call(thisArg, kValue, k, o)) {
                            return k;
                        }
                        // e. Increase k by 1.
                        k++;
                    }

                    // 7. Return -1.
                    return -1;
                }
            })
    }
}

export default polyfill