JS数组添加元素的三个方法

push(),在数组末尾添加

可以添加一个或者多个项目，返回的是添加后，数组的长度。

var arr = [];
var len = arr.push("a","b","c");  // 3

var arr = [];

var len = arr.push("a","b","c"); // 3

var a = [1,2,3];
var len = a.unshift(4,5);
// a: [4, 5, 1, 2, 3]
// len: 5

var a = [1,2,3];

var len = a.unshift(4,5);

// a: [4, 5, 1, 2, 3]

// len: 5

// 删除元素

var b = [1,2,3,4,5];
var removed_arr = b.splice(1,2);
// b: [1, 4, 5]
// removed_arr: [2, 3]

var b = [1,2,3,4,5];

var removed_arr = b.splice(1,2);

// b: [1, 4, 5]

// removed_arr: [2, 3]

// 添加元素

var b = [1,2,3,4,5];
var removed_arr = b.splice(3, 0, 8, 9, 10);

// b: [1, 2, 3, 8, 9, 10, 4, 5]
// removed_arr: []

var b = [1,2,3,4,5];

var removed_arr = b.splice(3, 0, 8, 9, 10);

// b: [1, 2, 3, 8, 9, 10, 4, 5]

// removed_arr: []

// 既有添加，又有删除

var b = [1,2,3,4,5];
var removed_arr = b.splice(3, 1, 8, 9, 10);
// b: [1, 2, 3, 8, 9, 10, 5]
// removed_arr: [4]

var b = [1,2,3,4,5];

var removed_arr = b.splice(3, 1, 8, 9, 10);

// b: [1, 2, 3, 8, 9, 10, 5]

// removed_arr: [4]