edx-platform/lms/static/js/ie11_find_array.js

// Polyfill for patching IE11 Browsers
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find#Polyfill

if (!Array.prototype.find) {
    Object.defineProperty(Array.prototype, 'find', { // eslint-disable-line no-extend-native
        value: function(predicate) {
            'use strict';

            var o, len, thisArg, k, kValue;

            // 1. Let O be ? ToObject(this value).
            if (this == null) {
                throw new TypeError('"this" is null or not defined');
            }

            o = Object(this);

            // 2. Let len be ? ToLength(? Get(O, "length")).
            // eslint-disable-next-line no-bitwise
            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.
            thisArg = arguments[1];

            // 5. Let k be 0.
            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 kValue.
                kValue = o[k];
                if (predicate.call(thisArg, kValue, k, o)) {
                    return kValue;
                }
                // e. Increase k by 1.
                k++;
            }

            // 7. Return undefined.
            return undefined;
        }
    });
}