/* 手写map方法 */
Array.prototype.myMap = function (fn, thisArg) {
if (typeof fn !== 'function') {
throw new Error(`${fn} is not function`)
}
let arr = this;
let newArray = [];
for (let i = 0; i < arr.length; i++) {
newArray[i] = fn.call(thisArg, arr[i], i, arr)
}
return newArray
}
/* 手写forEach */
Array.prototype.myForEach = function (fun, thisArg) {
if (typeof fun !== 'function') {
return new Error('params error')
}
if (!Array.isArray(this)) {
return `${this} is not array`
}
let oldArr = this;
for (var k = 0; k < oldArr.length; k++) {
console.log(thisArg)
fun.call(thisArg, oldArr[k], k, oldArr)
}
}
let arr = [1, 2, 3, 4]
let res = arr.myForEach((item, index) => { return arr[index] = item * 2 })
console.log(arr)
