js 数组的一些方法的原理

        Array.prototype.myForEach = function (callback) {
            if (Object.prototype.toString.call(callback).slice(8, -1) !== 'Function') {
                throw TypeError(`${callback} is not a function`);
            }
            for (let i = 0; i < this.length; i++) {
                callback.call(null, this[i], i, this);
            }
        };

        Array.prototype.myMap = function (callback) {
            if (Object.prototype.toString.call(callback).slice(8, -1) !== 'Function') {
                throw TypeError(`${callback} is not a function`);
            }
            const newArr = [];
            for (let i = 0; i < this.length; i++) {
                const newObj = callback.call(null, this[i], i, this);
                newArr.push(newObj);
            }
            return newArr;
        };

        Array.prototype.myFilter = function (callback) {
            if (Object.prototype.toString.call(callback).slice(8, -1) !== 'Function') {
                throw TypeError(`${callback} is not a function`);
            }
            let newArr = [];
            for (let i = 0; i < this.length; i++) {
                const res = callback.call(null, this[i], i, this);
                if (res) {
                    newArr.push(this[i]);
                }
            }
            return newArr;
        };

        Array.prototype.myReduce = function (callback, init) {
            if (Object.prototype.toString.call(callback).slice(8, -1) !== 'Function') {
                throw TypeError(`${callback} is not a function`);
            }
            let pre = init === undefined ? this[0] : init;
            for (let i = 0; i < this.length; i++) {
                const res = callback.call(null, pre, this[i], i, this);
                pre = res;
            }
            return pre;
        };

        Array.prototype.myFind = function (callback) {
            if (Object.prototype.toString.call(callback).slice(8, -1) !== 'Function') {
                throw TypeError(`${callback} is not a function`);
            }
            let obj;
            for (let i = 0; i < this.length; i++) {
                const res = callback.call(null, this[i], i, this);
                if (res) {
                    obj = this[i];
                    break;
                }
            }
            return obj;
        };

        Array.prototype.myEvery = function (callback) {
            if (Object.prototype.toString.call(callback).slice(8, -1) !== 'Function') {
                throw TypeError(`${callback} is not a function`);
            }
            let flag = false;
            for (let i = 0; i < this.length; i++) {
                const res = callback.call(null, this[i], i, this);
                if (!res) {
                    flag = true;
                }
            }
            if (flag) return false;
            return true;
        };

        Array.prototype.mySome = function (callback) {
            if (Object.prototype.toString.call(callback).slice(8, -1) !== 'Function') {
                throw TypeError(`${callback} is not a function`);
            }
            let flag = false;
            for (let i = 0; i < this.length; i++) {
                const res = callback.call(null, this[i], i, this);
                if (res) {
                    flag = true;
                }
            }
            if (flag) return true;
            return false;
        };