JavaScript Array 操作

其实以下操作，很多对于字符串同样适用。

shift:删除原数组第一项

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

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

 unshift:将参数添加到原数组开头，并返回数组的长度

var a = [1,2,3,4,5];   
var b = a.push(6,7); //a:[1,2,3,4,5,6,7] b:7

pop:删除原数组最后一项，并返回删除元素的值；如果数组为空则返回undefined 

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

push:将参数添加到原数组末尾，并返回数组的长度 

var a = [1,2,3,4,5];   
var b = a.push(6,7); //a:[1,2,3,4,5,6,7] b:7  

concat:返回一个新数组，是将参数添加到原数组中构成的  

var a = [1,2,3,4,5];   
var b = a.concat(6,7); //a:[1,2,3,4,5] b:[1,2,3,4,5,6,7]  

  

reverse:将数组反序 

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

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(2,2,7,8,9); //a:[1,2,7,8,9,5] b:[3,4]   

var b = a.splice(0,1); //同shift   

a.splice(0,0,-2,-1); var b = a.length; //同unshift   

var b = a.splice(a.length-1,1); //同pop   

a.splice(a.length,0,6,7); var b = a.length;  //同push

 sort(order function):按指定的参数对数组进行排序. 一般后面跟随一个排序的function，默认空置为从小到大排列

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

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

slice(start,end):返回从原数组中指定开始下标到结束下标之间的项组成的新数组  slice后可跟负值，例如slice.(-4, -1)

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

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

 join(separator):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("|"); //a:[1,2,3,4,5]  //b:"1|2|3|4|5"  

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

var a = [1,2,3,4,5];  
 
var b = a.join(""); //a:[1,2,3,4,5]  //b:"12345"