js数组方法filter的实现
const arr = [1,2,null,3];
Array.prototype._filter = function(cb) {
if (typeof cb !== 'function') {
throw new Error(`${cb} is not a Function`);
}
const that = [...this];
const newArr = [];
if(cb.constructor === Function) {
if(cb === Boolean) {
for(let i = 0, len = that.length; i<len; i++) {
const val = that[i];
if(val) {
newArr[newArr.length] = val;
}
}
return newArr;
}
return that;
}
for(let i = 0, len = that.length; i<len; i++) {
const condition = cb(that[i], i, this);
if (condition) {
newArr[newArr.length] = that[i];
}
}
return newArr;
}
const res = arr._filter(Boolean)
console.log(res)
// 输出结果：[1,2,3]const arr = [1,2,null,3];
Array.prototype._filter = function(cb) {
if (typeof cb !== 'function') {
throw new Error(`${cb} is not a Function`);
}
const that = [...this];
const newArr = [];
if(cb.constructor === Function) {
if(cb === Boolean) {
for(let i = 0, len = that.length; i<len; i++) {
const val = that[i];
if(val) {
newArr[newArr.length] = val;
}
}
return newArr;
}
return that;
}
for(let i = 0, len = that.length; i<len; i++) {
const condition = cb(that[i], i, this);
if (condition) {
newArr[newArr.length] = that[i];
}
}
return newArr;
}
const res = arr._filter(Boolean)
console.log(res)
// 输出结果：[1,2,3]
js数组方法shift的实现
Array.prototype._shift = function () {
const that = [...this];
for (let i = 0; i < that.length; i++) {
this[i] = this[i + 1]
}
this.length --;
return that[0]
}
const arr = [1, 2, 3];
console.log(arr._shift(), arr);
// 输出结果：1，[2,3]
js数组方法unshift的实现
Array.prototype._unshift = function (...arg) {
const arr = [...arg, ...this];
for (let i=0, len = arr.length; i < len; i++) {
this[i] = arr[i];
}
return this.length
}
const arr = [1, 2, 3];
console.log(arr._unshift(11,22,33), arr);
// 输出结果：6，[11, 22, 33, 1, 2, 3]
js数组方法pop的实现
Array.prototype._pop = function () {
const data = this[this.length - 1];
this.length --;
return data;
}
const arr = [1, 2, 3];
console.log(arr.pop(), arr);
// 输出结果：3，[1,2]
