22個(gè)超詳細(xì)的 JS 數(shù)組方法

var arr4 = [];   //創(chuàng)建一個(gè)空數(shù)組var arr5 = [20];   // 創(chuàng)建一個(gè)包含1項(xiàng)數(shù)據(jù)為20的數(shù)組var arr6 = ["lily","lucy","Tom"];   // 創(chuàng)建一個(gè)包含3個(gè)字符串的數(shù)組

var arr1 = new Array();   //創(chuàng)建一個(gè)空數(shù)組

var arr2 = new Array(20);   // 創(chuàng)建一個(gè)包含20項(xiàng)的數(shù)組

var arr3 = new Array("lily","lucy","Tom");   // 創(chuàng)建一個(gè)包含3個(gè)字符串的數(shù)組var array4 = new Array( 23 ); // ["23"]

let arr = Array.of(1, 2);console.log(arr.length);//2
let arr1 = Array.of(3);console.log(arr1.length);//1console.log(arr1[0]);//3
let arr2 = Array.of( 2 );console.log(arr2.length);//1console.log(arr2[0]);// 2

function arga(...args) {  //...args剩余參數(shù)數(shù)組,由傳遞給函數(shù)的實(shí)際參數(shù)提供    let arg = Array.from(args);    console.log(arg);}
arga( arr1 , 26,  from ); // [ arr1 ,26, from ]

function arga(...args) {       return Array.from(args, value => value + 1);}
let arr = arga( arr , 26,  pop );console.log(arr);//[ arr1 ,27, pop1 ]

const helper = {  diff: 1,  add(value) {    return value + this.diff;  }}
function translate() { //arguments 是一個(gè)對(duì)應(yīng)于傳遞給函數(shù)的參數(shù)的類數(shù)組對(duì)象  return Array.from(arguments, helper.add, helper); }
let arr = translate( liu , 26,  man );console.log(arr); // ["liu1", 27, "man1"]

var arr = [1,2,3];console.log(arr.join());   // 1,2,3console.log(arr.join("-"));   // 1-2-3console.log(arr);   // [1, 2, 3]（原數(shù)組不變）

function repeatString(str, n) {//一個(gè)長度為n+1的空數(shù)組用string去拼接成字符串,就成了n個(gè)string的重復(fù) return new Array(n + 1).join(str);}console.log(repeatString("abc", 3));   // abcabcabcconsole.log(repeatString("Hi", 5));   // HiHiHiHiHi

var arr = ["Lily","lucy","Tom"];var count = arr.push("Jack","Sean");console.log(count);  // 5console.log(arr);   // ["Lily", "lucy", "Tom", "Jack", "Sean"]var item = arr.pop();console.log(item);   // Seanconsole.log(arr);   // ["Lily", "lucy", "Tom", "Jack"]

var arr = ["Lily","lucy","Tom"];var count = arr.unshift("Jack","Sean");console.log(count);   // 5console.log(arr);   //["Jack", "Sean", "Lily", "lucy", "Tom"]var item = arr.shift();console.log(item);   // Jackconsole.log(arr);   // ["Sean", "Lily", "lucy", "Tom"]

var arr1 = ["a", "d", "c", "b"];console.log(arr1.sort());   // ["a", "b", "c", "d"]arr2 = [13, 24, 51, 3];console.log(arr2.sort());   // [13, 24, 3, 51]console.log(arr2);   // [13, 24, 3, 51](元數(shù)組被改變)

function compare(value1, value2) {    if (value1 < value2) {     return -1;    } else if (value1 > value2) {     return 1;    } else {     return 0;    }}arr2 = [13, 24, 51, 3];console.log(arr2.sort(compare));   // [3, 13, 24, 51]

function compare(value1, value2) {    if (value1 < value2) {     return 1;    } else if (value1 > value2) {     return -1;    } else {     return 0;    }}arr2 = [13, 24, 51, 3];console.log(arr2.sort(compare));   // [51, 24, 13, 3]

var arr = [13, 24, 51, 3];console.log(arr.reverse());   //[3, 51, 24, 13]console.log(arr);   //[3, 51, 24, 13](原數(shù)組改變)

var arr = [1,3,5,7];var arrCopy = arr.concat(9,[11,13]);console.log(arrCopy);   //[1, 3, 5, 7, 9, 11, 13]console.log(arr);   // [1, 3, 5, 7](原數(shù)組未被修改)

var arrCopy2 = arr.concat([9,[11,13]]);console.log(arrCopy2);   //[1, 3, 5, 7, 9, Array[2]]console.log(arrCopy2[5]);   //[11, 13]

var arr = [1,3,5,7,9,11];var arrCopy = arr.slice(1);var arrCopy2 = arr.slice(1,4);var arrCopy3 = arr.slice(1,-2);//相當(dāng)于arr.slice(1,4)var arrCopy4 = arr.slice(-4,-1);//相當(dāng)于arr.slice(2,5)console.log(arr);   //[1, 3, 5, 7, 9, 11](原數(shù)組沒變)console.log(arrCopy);   //[3, 5, 7, 9, 11]console.log(arrCopy2);   //[3, 5, 7]console.log(arrCopy3);   //[3, 5, 7]console.log(arrCopy4);   //[5, 7, 9]

var arr = [1,3,5,7,9,11];var arrRemoved = arr.splice(0,2);console.log(arr);   //[5, 7, 9, 11]console.log(arrRemoved);   //[1, 3]

var array1 = [22, 3, 31, 12];array1.splice(1, 0, 12, 35);  //[]
console.log(array1); // [22, 12, 35, 3, 31, 12]

const array1 = [22, 3, 31, 12];array1.splice(1, 1, 8);   //[3]
console.log(array1);  // [22, 8, 31, 12]

var arr = [1,3,5,7,7,5,3,1];console.log(arr.indexOf(5));   //2console.log(arr.lastIndexOf(5));   //5console.log(arr.indexOf(5,2));   //2console.log(arr.lastIndexOf(5,4));   //2console.log(arr.indexOf("5"));   //-1

var arr = [11, 22, 33, 44, 55];arr.forEach(function(x, index, a){ console.log(x +  |  + index +  |  + (a === arr));});
輸出為：
 11|0|true 22|1|true 33|2|true 44|3|true 55|4|true

var arr = [1, 2, 3, 4, 5];var arr2 = arr.map(function(item){ return item*item;});console.log(arr2);  //[1, 4, 9, 16, 25]

var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];var arr2 = arr.filter(function(x, index) { return index % 3 === 0 || x >= 8;});console.log(arr2);  //[1, 4, 7, 8, 9, 10]

let arr = [1, 2, 3,  cc , 5];arr.fill(1);console.log(arr);//[1,1,1,1,1];

let arr = [1, 2, 3,  arr , 5];
arr.fill(1, 2);console.log(arr);//[1,2,1,1,1]
arr.fill(0, 1, 3);console.log(arr);//[1,0,0,1,1];

var arr = [1, 2, 3, 4, 5];var arr2 = arr.every(function(x) { return x < 10;});console.log(arr2);  //truevar arr3 = arr.every(function(x) { return x < 3;});console.log(arr3);  // false

var arr = [1, 2, 3, 4, 5];var arr2 = arr.some(function(x) { return x < 3;});console.log(arr2);  //truevar arr3 = arr.some(function(x) { return x < 1;});console.log(arr3);  // false

const array1 = [22, 3, 31, 12,  arr ];const includes = array1.includes(31);console.log(includes); // true
const includes1 = array1.includes(31, 3); // 從索引3開始查找31是否存在console.log(includes1); // false

let values = [1, NaN, 2];console.log(values.indexOf(NaN));//-1console.log(values.includes(NaN));//true

var values = [1,2,3,4,5];var sum = values.reduceRight(function(prev, cur, index, array){return prev + cur;},10);   //數(shù)組一開始加了一個(gè)初始值10,可以不設(shè)默認(rèn)0console.log(sum);  //25

const array1 = [22, 3, 31, 12];const str = array1.toLocaleString();const str1 = array1.toString();
console.log(str); // 22,3,31,12console.log(str1); // 22,3,31,12

let arr = [1, 2, 3,  arr , 5, 1, 9];
console.log(arr.find((value, keys, arr) => {    return value > 2;})); // 3 返回匹配的值
console.log(arr.findIndex((value, keys, arr) => {    return value > 2;})); // 2 返回匹配位置的索引

//將數(shù)組的前兩個(gè)元素復(fù)制到數(shù)組的最后兩個(gè)位置let arr = [1, 2, 3,  arr , 5];
arr.copyWithin(3, 0);console.log(arr);//[1,2,3,1,2]

let arr = [1, 2, 3,  arr , 5, 9, 17];
//從索引3的位置開始粘貼//從索引0的位置開始復(fù)制//遇到索引3時(shí)停止復(fù)制arr.copyWithin(3, 0, 3);console.log(arr);//[1,2,3,1,2,3,17]

const arr1 = [0, 1, 2, [3, 4]];
console.log(arr1.flat());// expected output: [0, 1, 2, 3, 4]
const arr2 = [0, 1, 2, [[[3, 4]]]];
console.log(arr2.flat(2));// expected output: [0, 1, 2, [3, 4]]
//使用 Infinity，可展開任意深度的嵌套數(shù)組var arr4 = [1, 2, [3, 4, [5, 6, [7, 8, [9, 10]]]]];arr4.flat(Infinity);// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
// 扁平化數(shù)組空項(xiàng),如果原數(shù)組有空位，flat()方法會(huì)跳過空位var arr4 = [1, 2, , 4, 5];arr4.flat();// [1, 2, 4, 5]

// 相當(dāng)于 [[2, 4], [3, 6], [4, 8]].flat()[2, 3, 4].flatMap((x) => [x, x * 2])// [2, 4, 3, 6, 4, 8]

for (let index of [ a ,  b ].keys()) {  console.log(index);  }  // 0  // 1  for (let elem of [ a ,  b ].values()) {  console.log(elem);  }  //  a   //  b   for (let [index, elem] of [ a ,  b ].entries()) {  console.log(index, elem);  }  // 0 "a"  // 1 "b"

let letter = [ a ,  b ,  c ];  let entries = letter.entries();  console.log(entries.next().value); // [0,  a ]  console.log(entries.next().value); // [1,  b ]  console.log(entries.next().value); // [2,  c ]