数组: push()、pop()、shift()、unshift()、slice()、splice()、join()、reverse()、sort()、concat()
1.push():直接操作数组,在数组的尾部插入,返回的新的数组的长度
<script>
var arr=["a","b","c","d"];
console.log(arr.push("e"));
</script>
2.pop():直接操作数组,在数组的尾部删除元素,返回这个被删除的元素
console.log(arr.pop());
3.shift():直接操作数组,在数组的头部删除,返回被删除的元素
console.log(arr.shift());
4.unshift():直接操作数组,在数组的头部插入,返回的新的数组的长度
console.log(arr.unshift("f"));
5、concat():不直接操作数组,而是返回一个新的数组,用于连接若干个数组或者是若干个元素
console.log(arr.concat("g"));
console.log(arr.concat(["h","i"]));
6.slice():不直接操作数组,用于从数组中取出某几项。(start,end)不包括end,一共取出end-start项。也可以只写slice(3)表示从第三项开始取到最后
console.log(arr.slice(1,3));
console.log(arr.slice(3));
7、reverse():直接操作数组,将数组中的元素倒序。
var arr = ["A","B","C","D","E","F","G"];
arr.reverse(); //不需要赋值
console.log(arr); //["G", "F", "E", "D", "C", "B", "A"]
8,join()
var arr = [1,2,3,4,5,6,7];
var str = arr.join("★");
console.log(str);
var str = arr.join(分隔符); |
如果不写分隔符,那么等价于用逗号分开
|
9、 多功能splice()插入、删除、替换
1. 下面的情况:splice直接作用于数组,返回的值是被替换的人
var arr = ["A","B","C","D","E","F","G"];
console.log(arr.splice(3,2,"斑马","骆驼"));
console.log(arr);// ["A", "B", "C", "斑马", "骆驼", "F", "G"]
2.从第三项开始,连续 选择两项修改为新的四项
var arr = ["A","B","C","D","E","F","G"];
arr.splice(3,2,"X","Y","Z","思密达"); //从数组下标为3开始这项,连数2项,改为……
console.log(arr);
3.相当于在第二项的后面插入了两项
var arr = ["A","B","C","D","E","F","G"];
arr.splice(2,0,"嘻嘻","哈哈"); //插入到下标为2的项前,不删除项目
console.log(arr);
4.删除数组的后个几项
arr.splice(-8);
10、排序sort()
var arr = ["G","A","C","B","I","H","G","I","B"];
arr.sort();
console.log(arr);
结果:
//sort函数默认是按照字符顺序排的,隐式将数字转为string
//比字符编码顺序
var arr = [23,435,456,23,2,345,2,32,11,324,32,43,65,667,78,43];
arr.sort();
console.log(arr);
结果:
sort(function(a,b){})的应用:return 1代表需要换位置,return -1代表不需要换位置。
var arr=[32,32,2,32,3,2,2,3,232,3,2,3,2,33,1,3,4234,33];
arr.sort(function(a,b){
if(a>b)
{
return 1
}
else if(a<b)
{
return -1
}
else
{
return 0
}
})
console.log(arr);