rebuilt-arr-prototypes.js

Array.prototype.filter = function (callback) {
    const arr = this;

    const returnedVal = [];
    for (const i = 0; i < arr.length; i++) {
        const exist = callback(arr[i], i, arr);
        if (exist) {
            returnedVal.push(arr[i]);
        }
    }

    return returnedVal;
};

Array.prototype.map = function (callback) {
    const arr = this;

    const returnedVal = [];
    for (const i = 0; i < arr.length; i++) {
        const exist = callback(arr[i], i, arr);
        returnedVal.push(exist);
    }

    return returnedVal;
}

Array.prototype.forEach = function (callback) {
    const arr = this;

    for (const i = 0; i < arr.length; i++) {
        callback(arr[i], i, arr);
    }
};