1、添加元素
函数：push(para)，参数说明para要添加的元素
示例：
var lang = ["php","java","javascript"];
lang.push('.net');
结果：lang = ["php","java","javascript",".net"];
2、删除和替换元素
函数：splice(para1,para2,para3)，参数说明para1其实位置（从0开始），para2要删除的元素个数，para3（可选）要替换的元素
示例：
a、删除
var lang = ["php","java","javascript"];
lang.splice(0,1);
结果：lang = ["java","javascript",".net"];
b、替换
var lang = ["php","java","javascript"];
lang.splice(0,1,'.net');
结果：lang = [".net","javascript",".net"];
