【引用类型】转换方法

 1 <script>
 2     var arr1 = ["a","b","c"];
 3 
 4     //toString
 5     //输出一个字符串。将数组中每一个值用逗号隔开输出
 6     alert(arr1.toString());                //输出：a,b,c
 7 
 8     //valueOf()
 9     //与调用toString()结果一样。alert()要接收字符串参数，所以回在后台调用toString()方法
10     alert(arr1.valueOf());                //输出：a,b,c
11     //返回数组
12     console.log(arr1.valueOf());        //输出：(3) ["a", "b", "c"]
13 
14     //toLocaleString()
15     //通常调用toLocaleString()方法,返回跟toString()、valueOf()一样的值
16     alert(arr1.toLocaleString());        //输出：a,b,c
17     //调用数组的toLocaleString()方法，调用的是每一项的toLocaleString()方法
18     var arr1 = {
19         toLocaleString : function(){
20             return "a";
21         },
22         toString : function(){
23             return "apple";
24         }
25     };
26     var arr2 = {
27         toLocaleString : function(){
28             return "b";
29         },
30         toString : function(){
31             return "banana";
32         }
33     };
34     var arr = [arr1,arr2];
35     alert(arr);                            //输出：apple,banana
36     alert(arr.toString());                //输出：apple,banana
37     alert(arr.toLocaleString());        //输出：a,b
38 </script>

1 <script>
2     var arr1 = ["a","b","c",undefined,null];
3     console.log(arr1.join(","));        //输出：a,b,c,,
4     console.log(arr1.join("||"));        //输出：a||b||c||||
5     console.log(arr1.join());            //输出：a,b,c,,
6     console.log(arr1.join(undefined));    //输出：a,b,c,,
7     console.log(arr1.join(null));        //输出：anullbnullcnullnull
8 </script>