study-overview/src/util/polyfills.js

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if (typeof Object.assign != 'function') {
    Object.defineProperty(Object, 'assign', {
        value: function assign(target, varArgs) {
            // .length of function is 2
            'use strict';

            if (target == null) {
                // TypeError if undefined or null
                throw new TypeError('Cannot convert undefined or null to object');
            }

            var to = Object(target);

            for (var index = 1; index < arguments.length; index++) {
                var nextSource = arguments[index];

                if (nextSource != null) {
                    // Skip over if undefined or null
                    for (var nextKey in nextSource) {
                        // Avoid bugs when hasOwnProperty is shadowed
                        if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
                            to[nextKey] = nextSource[nextKey];
                        }
                    }
                }
            }

            return to;
        },
        writable: true,
        configurable: true
    });
}

if (!Array.prototype.find) {
    Object.defineProperty(Array.prototype, 'find', {
        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 kValue.
                var kValue = o[k];
                if (predicate.call(thisArg, kValue, k, o)) {
                    return kValue;
                }
                // e. Increase k by 1.
                k++;
            }

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

if (!Array.prototype.includes) {
    Object.defineProperty(Array.prototype, 'includes', {
        value: function(valueToFind, fromIndex) {
            if (this == null) {
                throw new TypeError('"this" is null or not defined');
            }

            // 1. Let O be ? ToObject(this value).
            var o = Object(this);

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

            // 3. If len is 0, return false.
            if (len === 0) {
                return false;
            }

            // 4. Let n be ? ToInteger(fromIndex).
            //        (If fromIndex is undefined, this step produces the value 0.)
            var n = fromIndex | 0;

            // 5. If n = 0, then
            //    a. Let k be n.
            // 6. Else n < 0,
            //    a. Let k be len + n.
            //    b. If k < 0, let k be 0.
            var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);

            function sameValueZero(x, y) {
                return (
                    x === y ||
                    (typeof x === 'number' && typeof y === 'number' && isNaN(x) && isNaN(y))
                );
            }

            // 7. Repeat, while k < len
            while (k < len) {
                // a. Let elementK be the result of ? Get(O, ! ToString(k)).
                // b. If SameValueZero(valueToFind, elementK) is true, return true.
                if (sameValueZero(o[k], valueToFind)) {
                    return true;
                }
                // c. Increase k by 1.
                k++;
            }

            // 8. Return false
            return false;
        }
    });
}

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;
        }
    });
}