【关于数组】JavaScript常用的API

shift:删除数组的第一项，并返回删除元素的值

var arr1 = [1,2,3,4,5];
var b = arr1.shift();
console.log(arr1);  //[2,3,4,5]
console.log(b);     //1

pop:删除原数组的最后一项，并返回删除元素的值

var arr1 = [1,2,3,4,5];
var b = arr1.pop(); 
console.log(arr1); //[1,2,3,4]
console.log(b);    //5

unshift:向数组头部追加，返回数组长度

var arr1 = [1,2,3];
var b = arr1.unshift(4,5,6);
console.log(arr1); //[4,5,6,1,2,3]
console.log(b);    // 6

push:将参数添加到数组尾部，返回数组长度

var arr1 = [1,2,3];
var b = arr1.push(4,5,6);
console.log(arr1); //[1,2,3,4,5,6]
console.log(b);    // 6

concat：返回一个新数组，是将参数添加到原数组中构成的

arr = ['A'];
var b = arr.concat(6,7);  
console.log(b); // ['A',6,7]

splice(start,deleteCount,val1,val2,)：从start位置开始删除deleteCount项，并从该位置起插入val1,val2,

var a = [1,2,3,4,5];
var b = a.splice(2,1,111,222,333); 
console.log(a); //[ 1, 2, 111, 222, 333, 4, 5 ]
console.log(b); //[3] 返回被删除的内容

slice(start,end);截取字符串 返回截取的从开始下标到结束下标之间的项组成的新数组

var a = [1,2,3,4,5];   
var b = a.slice(2,5);  
console.log(a);  //[1,2,3,4,5]
console.log(b);  //[3,4,5]

join(separator) 数组切割，返回字符串 将数组的元素组起一个字符串，以separator为分隔符，省略的话则用默认用逗号为分隔符

var a = [1,2,3,4,5];   
var b = a.join('|');  
console.log(a); //a：[1,2,3,4,5]
console.log(b); //b："1|2|3|4|5"