一. 实现Array.isArray
if (!Array.isArray){
Array.isArray = function(arg){
return Object.prototype.toString.call(arg) === '[object Array]';
};
}二. 将类数组转换为数组
1. 借用数组的方法进行转换
// 1. slice Array.prototype.slice.call(arguments) // 2. concat [].concat.apply([], arguments)
2. es6的方式转换
// 1. ...扩展运算符 [...arguments] // 2. Array.from() Array.from(arguments)
三. 判断是否为数组
var a = []; // 1.基于instanceof a instanceof Array; // 2.基于constructor a.constructor === Array; // 3.基于Object.prototype.isPrototypeOf Array.prototype.isPrototypeOf(a); // 4.基于getPrototypeOf Object.getPrototypeOf(a) === Array.prototype; // 5.基于Object.prototype.toString Object.prototype.toString.call(a) === '[object Array]'; // 6. 通过Array.isArray Array.isArray(a)
四. 数组方法实现
1.forEach
Array.prototype.myForEach = function(fn, context = window){
let len = this.length
for(let i = 0; i < len; i ){
typeof fn === 'function' && fn.call(context, this[i], i)
}
}2. filter
Array.prototype.myFilter = function(fn, context = window){
let len = this.length,
result = []
for(let i = 0; i < len; i ){
if(fn.call(context, this[i], i, this)){
result.push(this[i])
}
}
return result
}3. every
Array.prototype.myEvery = function(fn, context){
let result = true,
len = this.length
for(let i = 0; i < len; i ){
result = fn.call(context, this[i], i, this)
if(!result){
break
}
}
return result
}4. some
Array.prototype.mySome = function(fn, context){
let result = false,
len = this.length
for(let i = 0; i < len; i ){
result = fn.call(context, this[i], i, this)
if(result){
break
}
}
return result
}5. findIndex
Array.prototype.myFindIndex = function (callback) {
for (let i = 0; i < this.length; i ) {
if (callback(this[i], i)) {
return i
}
}
}6. Reduce
Array.prototype.myReduce = function (fn, initialValue) {
let arr = Array.prototype.call(this)
let res, startIndex
res = initialValue ? initialValue : arr[0]
startIndex = initialValue ? 0 : 1
for (let i = startIndex; i < arr.length; i ) {
res = fn.call(null, res, arr[i], i, this)
}
return res
}五. 实现数组扁平化
let ary = [1, [2, [3, 4, 5]]]
1. 普通递归 concat
const flatten = function(ary){
let result = []
for(let i = 0;i<ary.length;i ){
if(Array.isArray(ary[i])){
result = result.concat(flatten(ary[i]))
} else {
result.push(ary[i])
}
}
return result
}2. reduce concat
const flatten = function(ary){
return ary.reduce((prev, next)=>{
return prev.concat(Array.isArray(next) ? flatten(next) : next)
}, [])
}3. while concat
const flatten = function(ary){
while(ary.some(item=>Array.isArray(item))){
ary = [].concat(...ary)
}
return ary
}4. toString split
const flatten = function(ary){
return ary.toString().split(',')
}5. flat
const flatten = function(ary){
return ary.flat(Infinity)
}6. 正则
const flatten6 = function(ary){
let str = JSON.stringify(ary)
str = str.replace(/([|])/g, '')
return JSON.parse(`[${str}]`)
}六. 去重
1. 利用 ES6 语法（扩展运算符）
const unique1 = (array) => {
// return Array.from(new Set(array))
return [...new Set(array)]
}2. 利用 forEach() 对象容器
const unique2 = (array) => {
const arr = []
const obj = {}
array.forEach(item => {
if (!obj.hasOwnProperty(item)) {
obj[item] = true
arr.push(item)
}
})
return arr
}3. 利用 forEach 和 indexOf
const unique3 = (array) => {
const arr = []
array.forEach(item => {
if (arr.indexOf(item) === -1) {
arr.push(item)
}
})
return arr
}4. 利用 filter indexOf
const unique4 = (array) => {
return array.filter((item,index) => {
return array.indexOf(item) === index;
})
}5. 利用 forEach 和 includes (本质同3)
const unique6 = (array) => {
let result = [];
array.forEach(item => {
if(!result.includes(item)){
result.push(item);
}
})
return result;
}6. 利用 sort
const unique6 = (array) => {
let result = array.sort(function (a,b) {
return a - b;
});
for(let i = 0;i < result.length;i ){
if(result[i] === result[i 1]){
result.splice(i 1,1);
i --;
}
}
return result;
}7. 双层for循环
function unique(array) {
// res用来存储结果
var res = [];
for (var i = 0, arrayLen = array.length; i < arrayLen; i ) {
for (var j = 0, resLen = res.length; j < resLen; j ) {
if (array[i] === res[j]) {
break;
}
}
// 如果array[i]是唯一的，那么执行完循环，j等于resLen
if (j === resLen) {
res.push(array[i])
}
}
return res;
}
console.log(unique(array)); // [1, "1"]七. 排序
1. 冒泡排序
原理：利用数组的前一项与相邻的后一项相比较，判断大/小，交换位置
const bubbleSort = function(ary){
for(let i = 0; i < ary.length - 1; i ){
for(let j = 0; j < ary.length - 1 - i; j ){
if(ary[j] > ary[j 1]){
[ary[j], ary[j 1]] = [ary[j 1], ary[j]]
}
}
}
return ary
}2. 选择排序
原理：利用数组的某项与后面所有的值相比较，判断大/小，交换位置
const bubbleSort = function(ary){
for(let i = 0; i < ary.length - 1; i ){
for(let j = i 1; j < ary.length; j ){
if(ary[i] > ary[j]){
[ary[i], ary[j]] = [ary[j], ary[i]]
}
}
}
return ary
}3. 原生排序
Array.sort((a, b)=>a-b)
4. 快速排序
原理：取数组的中间值作为基准，判断左右两边的值大或小，添加到相应数组，递归调用，然后将所有的值拼接在一起。
const quick_sort = function(ary){
if(ary.length < 1){
return ary
}
let centerIndex = Math.floor(ary.length/2)
let centerVal = ary.splice(centerIndex, 1)[0]
let left = []
let right = []
ary.forEach(item => {
item > centerVal ? right.push(item) : left.push(item)
})
return [...quick_sort(left), ...[centerVal], ...quick_sort(right)]
}5. 插入排序
原理：先将数组中的一项添加到新数组中，循环数组每一项与新数组中比较，比较大的值放在后面小的放到新数组的前面。
const insertion_sort = function(ary){
let newAry = ary.splice(0, 1)
for(let i = 0; i < ary.length; i ){
let cur = ary[i]
for(let j = newAry.length - 1; j >= 0;){
if(cur < newAry[j]){
j--
j === -1 && newAry.unshift(cur)
} else {
newAry.splice(j 1, 0, cur)
j = -1
}
}
}
return [...newAry]
}八. 最大值与最小值
1. 假设法
const maxMin = function(ary){
let [min, max] = [ary[0], ary[1]]
ary.forEach(ele => {
min > ele ? min = ele : null
max < ele ? max = ele : null
})
return [min, max]
}2. math.max() 假设法
var arr = [6, 4, 1, 8, 2, 11, 23];
var result = arr[0];
for (var i = 1; i < arr.length; i ) {
result = Math.max(result, arr[i]);
}
console.log(result);3. reduce
var arr = [6, 4, 1, 8, 2, 11, 23];
function max(prev, next) {
return Math.max(prev, next);
}
console.log(arr.reduce(max));4. 排序
var arr = [6, 4, 1, 8, 2, 11, 23];
arr.sort(function(a,b){return a - b;});
console.log(arr[arr.length - 1])5. 利用Math.max
Math.max.apply(null, ary)
// 扩展运算符
Math.max(...arr)
// eval
var max = eval("Math.max(" arr ")");九. 平均值
const balance = function(ary){
ary.sort((a, b) => a - b)
ary.shift()
ary.pop()
let num = 0
ary.forEach(item => {
num = item
})
return (num/ary.length).toFixed(2)
}十. 数组乱序
function shuffle(a) {
var j, x, i;
for (i = a.length; i; i--) {
j = Math.floor(Math.random() * i);
x = a[i - 1];
a[i - 1] = a[j];
a[j] = x;
}
return a;
}十一. 将数组扁平化并去除其中重复数据，最终得到一个升序且不重复的数
let arr = [ [1, 2, 2], [3, 4, 5, 5], [6, 7, 8, 9, [11, 12, [12, 13, [14] ] ] ], 10];
Array.from(new Set(arr.flat(Infinity))).sort((a,b)=>{ return a-b})到此这篇关于一文掌握JavaScript数组常用工具函数总结的文章就介绍到这了,更多相关JS数组工具内容请搜索Devmax以前的文章或继续浏览下面的相关文章希望大家以后多多支持Devmax！