1. pop()
Array.prototype.myPop = function () {
var lastchild = this[this.length - 1] //理解这两个this
// var data = this
// var lastchild = data[data.length - 1]
if (this.length == 0) {
return undefined
} else{
this.length--
}
return lastchild
}
const arr = [1,2,3,4,5];
var a = arr.myPop();
console.log(a,arr); // 5 [ 1, 2, 3, 4 ]
2. push()
Array.prototype.myPush = function () {
var newlen = this.length + arguments.length;
for ( i = 0; i < arguments.length; i++) {
this[newlen - arguments.length + i] = arguments[i];
// 等价于 this[this.length] = arguments[i];
}
return newlen;
}
var arr = [1, 3, 5];
var a = arr.myPush(7, 9, 11);
console.log(a, arr); // 6 [1, 3, 5, 7, 9, 11]
ECMAScript中的参数在内部是用一个数组来表示的。在函数体内可以通过arguments对象来访问这个参数数组，从而获取传递给函数的每一个参数。
3. shift()
Array.prototype.myShift = function () {
const first = this[0];
for (let i = 0; i < this.length; i++) {
this[i] = this[i + 1];
}
this.length--;
return first
}
const arr = [1, 3, 5, 7, 9];
const a = arr.myShift();
console.log(a, arr); // 1 [ 3, 5, 7, 9 ]
4. unshift()
Array.prototype.myUnshift = function () {
var newlen = this.length + arguments.length;
for (i = newlen-1; i >= 0; i--) {
if (i > arguments.length - 1) {
this[i] = this[i - arguments.length]
}
else {
this[i] = arguments[i];
}
}
return newlen;
}
var arr = [1, 3, 5];
var a = arr.myUnshift(8, 1, 8);
console.log(a, arr); // [8, 1, 8, 1, 3, 5]
5. sort()
quickSort
function quickSort(nums) {
if (nums.length <= 1) {
return nums
}
let pivotIndex = Math.floor(nums.length / 2)
let pivot = nums.splice(pivotIndex, 1)[0]
let left = [],
right = []
nums.forEach((element) => {
if (element < pivot) {
left.push(element)
} else {
right.push(element)
}
})
return quickSort(left).concat(pivot, quickSort(right))
}
let nums = [8, 1, 8, 5, 2, 0]
console.log(quickSort(nums)); // [ 0, 1, 2, 5, 8, 8 ]
bubbleSort
function swap(myArray,p1,p2){
var temp = myArray[p1]
myArray[p1] = myArray[p2]
myArray[p2] = temp
}
function bubbleSort(myArray){
let len = myArray.length - 1
for(i = 0; i < len; i++){
for(j = 0; j < len - i; j++){
if(myArray[j] > myArray[j + 1]){
swap(myArray, j, j + 1)
}
}
}
return myArray
}
var nums = [8, 1, 2, 5, 0]
console.log(bubbleSort(nums)); // [ 0, 1, 2, 5, 8 ]
selectionSort
function selectionSort(nums){
let len = nums.length
let min = 0
let temp
nums.forEach((element,i) => {
min = i
for(j = i + 1; j < len; j++){
if(nums[j] < nums[min]){
min = j
}
}
temp = nums[i]
nums[i] = nums[min]
nums[min] = temp
})
return nums
}
let nums = [2,9,6,8,1,4]
console.log(selectionSort(nums));
6. slice()
Array.prototype.mySlice = function(start,end){
let result = []
for(i = start; i < end; i++){
result.push(this[i])
}
return result
}
let arr = [2,9,9,6,8,1,4]
let result = arr.mySlice(2,5)
console.log(result); // [9, 6, 8]
7. indexOf()
Array.prototype.myIndexOf = function(item, start = 0){
for(let i = start; i < this.length; i++){
if(item == this[i]) return i;
}
return -1;
}
let arr = ["Banana","Orange","Apple","Mango","Banana","Orange","Apple"];
let result = arr.myIndexOf("Apple", 3)
console.log(result) // 6
8. some()
Array.prototype.mySome = function (foo, obj) {
for (i = 0; i < this.length; i++) {
//call(obj, this[i]) bind(obj)(this[i])
if (obj ? foo.apply(obj, [this[i]]) : foo(this[i])) {
return true;
}
}
return false;
}
var arr = [1, 3, 5, 7];
var result = arr.mySome(function(i) {
console.log(this);
return i > 5
}, {a: 'a'})
console.log(result);
注意：if (obj ? foo.apply(obj, [this[i]]) : foo(this[i]))。这条语句主要是为了实现 thisArg 这个API功能：改变回调函数内的this指向。
arr.some(callback(element[, index[, array]])[, thisArg] )
[参数]
callback用来测试每个元素的函数，接受三个参数：element数组中正在处理的元素。index（可选） 数组中正在处理的元素的索引值。array（可选）some()被调用的数组。thisArg（可选）执行callback时使用的this值。
9. every()
Array.prototype.myEvery = function (foo, obj) {
for (i = 0; i < this.length; i++) {
// (!(obj?foo.bind(obj)(this[i]) :foo(this[i])))
if (!(foo.bind(obj)(this[i])) ){
return false;
}
}
return true;
}
var arr = [1, 3, 5, 7];
var result = arr.myEvery(i => i > 5)
console.log(result); // false
10. map()
Array.prototype.myMap = function(fn){
let data = []
for(let i = 0; i < this.length; i++){
data.push(fn(this[i], i, this))
// data.push(fn.call(this[i], i))
}
return data
}
console.log([1,2,3].myMap((item, i, arr) => {
console.log(i);
console.log(arr);
return item * item
}));
11. filter()
const data = [1, 2, 3, 4, 5].filter(i => i < 3)
Array.prototype.myFilter = function (fn) {
const data = [];
for (let key in this) {
fn.call(null, this[key]) && data.push(this[key])
}
return data;
}
const data1 = [1,2,3,4,5].myFilter(i => i <= 3)
console.log(data1) // [1, 2, 3]
