2022-06-30

常用的数组API

1、toString() — 将数组转化为字符串（对象数组不可用）

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let arr = [1,2,3,4,5];

arr.toString(); // "1,2,3,4,5"

2、arr.join() — 将所有元素放入一个字符串中（对象数组不可用）

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var arr = ["Banana", "Orange", "Apple", "Mango"];

arr.join(); // "Banana, Orange, Apple, Mango"

3、arr.concat(arr2, arr3, …) — 将多个数组拼接在一起

var arr1 = ["Cecilie", "Lone"];

var arr2 = ["Emil", "Tobias", "Linus"];

var arr3 = ["Robin"];

let arr = arr1.concat(arr2,arr3); // ['Cecilie', 'Lone', 'Emil', 'Tobias', 'Linus', 'Robin']

4、arr.slice(“开始的下标”, “结束的下标”) — 返回一个子数组

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var arr1 = [“Banana”, “Orange”, “Lemon”, “Apple”, “Mango”];

var arr = arr1.slice(1,3); // [“Orange”, “Lemon”]

5.1、 arr.indexOf() — 返回这个值在数组中出现的下标

5.2、arr.lastIndexOf() — 搜索数组中的元素，并返回它最后出现的位置。

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var fruits = ["Banana", "Orange", "Apple", "Mango"];

var a = fruits.indexOf("Apple"); // 2

6、arr.splice(“开始下标”, “连续几个”) — 从数组中添加或删除元素。

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var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.splice(2,0,"Lemon","Kiwi"); // ['Banana', 'Orange', 'Lemon', 'Kiwi', 'Apple', 'Mango']

7、arr.reverse() — 将数组里的值前后颠倒

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var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.reverse(); // ['Mango', 'Apple', 'Orange', 'Banana']

8、arr.sort() — 对数组里的值进行排序

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var points = [40,100,1,5,25,10];

points.sort(function(a,b){return a-b}); // [1,5,10,25,40,100]

9、arr.pop() — 删除数组最后一个值

var fruits = [“Banana”, “Orange”, “Apple”, “Mango”];

fruits.pop(); // [“Banana”];

fruits; // [“Orange”, “Apple”, “Mango” ];

10、arr.push(“值”) — 从尾部添加一个新值

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var fruits = [“Banana”, “Orange”, “Apple”, “Mango”];

fruits.push(“Kiwi”); // [‘Banana’, ‘Orange’, ‘Apple’, ‘Mango’, ‘Kiwi’]

11、arr.shift() — 删除数组第一个值

var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.shift(); // ["Banana"]

fruits; //['Orange', 'Apple', 'Mango']

12、arr.unshift() — 从头部添加一个新值

var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.unshift("Lemon","Pineapple");

fruits; // ['Lemon', 'Pineapple', 'Banana', 'Orange', 'Apple', 'Mango']

13、Array.isArray(arr) — 判断对象是否为数组。

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