var arr = [1,2,3,4,5,6,7,8,9];     /*通过下标取值和赋值*/
arr[0]
arr[3] = 3

arr.length      /*赋值过小值, 元素就会丢失*/

var arr = [0,1]; 
arr.indexOf(2);  /*输出1  字符串"1"和数字1是不同的*/

$ slice()   /*类似于String中的substring*/

push:    /*压入到头部*/
shift:   /*弹出头部的一个元素*/

(3)["B","A","C"]         /*排序前*/
arr.sort()         
(3)["A","B","C"]         /*排序后*/

(3)["B","A","C"]         /*反转前*/
arr.reverse()        
(3)["C","B","A"]         /*反转后*/

(3)["C","B","A"]
arr.concat([1,2,3])        
(6)["C","B","A",1,2,3]
arr
(3)["C","B","A"]

(3)["C","B","A"] 
arr.join('-')         /*使用特定的字符串连接*/   
/*结果输出"C-B-A"*/       

arr = [[1,2],[3,4],["5","6"]];
arr[1][1]   
/*结果输出4*/