JavaScript的数组详解

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• 创建数组

1.通过new Array()进行创建

var arr1=new Array();

2.通过中括号进行创建

var arr2=[];

• 计算数组的长度

var arr3=['1','2','3'];
console.log(arr3.length)

• 数组的下标

//从0开始，从左到右
var arr4 = ["a","b","c","d"];
console.log(arr4[1])

注意：下标为-1表示没有这个元素，而不是倒数第一个！

• 获取成员在数组中的下标 indexOf

var arr=["a","b","c"];
console.log(arr.indexOf("b"))
console.log(arr.indexOf("1"))
 
输出：
1
-1  //当成员不在数组中，则返回-1

• 数组的拼接 join

var arr5=["a","b","c"];
console.log(arr5.join("-"))
 
输出：
a-b-c

• 数组的反转排列

var arr5=["a","b","c"];
console.log(arr5.reverse())
 
输出：
["c", "b", "a"]

• 数组的删除元素

splice(删除开始的下标，删除的成员个数)
返回值就是被删除的元素组成的数组

var arr5=["a","b","c","d"];
console.log(arr5.splice(1,2))
console.log(arr5)
 
输出：
["b","c"]
["a","d"]

• 在数组的任意位置添加元素

splice(要插入的下标位置，，[插入的元素])

var arr5=["a","b","c","d"];
console.log(arr5.splice(1,0,"x","y","z"))  //0表示不删除元素！1表示插入的位置！
console.log(arr5)
 
输出：
[]  //表示没有删除的元素
["a", "x", "y", "z", "b", "c", "d"]  //在下标为1的地方插入"x","y","z

• 在数组的末尾添加元素

push 表示给数组新增成员，返回结果是新的成员的数量！

var arr5=["a","b","c",];
var ret=arr5.push("d");
console.log(arr5)
console.log(ret)
 
输出：
["a", "b", "c", "d"]
4

• 移除数组的最后一个成员

pop，返回值是被移除的元素！

var arr5=["a","b","c"];
var ret=arr5.pop();
console.log(ret)
console.log(arr5)
 
输出：
c
["a", "b"]

• 多维数组

多维数组就是数组的嵌套。二维数组就是嵌套两层，三维数组就是嵌套三层。

var arr5=[
        ["a","b","c"],
        ["1","2","3"],
        ["x","y","z"]
        ]

• 多维数组成员的获取

var arr5=[
        ["a","b","c"],
        ["1","2","3"],
        ["x","y","z"]
        ]
        console.log(arr5[1][2])
 
输出：
3