引用方法操作方法

Posted 2021-03-10 xiaoxustudy

 1 <script>
 2     var arr1 = ["a","b","c",undefined,null];
 3     //concat()
 4     //创建数组副本，将接收到的参数添加到副本末尾
 5     var arr2 = arr1.concat("d","e");
 6     console.log(arr1);    //输出：(5) ["a", "b", "c", undefined, null]
 7     console.log(arr2);    //输出：(7) ["a", "b", "c", undefined, null, "d", "e"]
 8 
 9     //slice()
10     //返回指定位置的项
11     //接收1个参数
12     console.log(arr1.slice(1));         //输出：(4) ["b", "c", undefined, null]
13     //接收2个参数
14     console.log(arr1.slice(1,3));     //输出：(2) ["b", "c"]
15     //参数为负数。用数组长度加上该数来确定相应的位置
16     console.log(arr1.slice(-4,-2));     //输出：(2) ["b", "c"]
17 
18     //splice()
19     //删除任意数量的项
20     //splice(要删除的第一项的位置，要删除的项数)
21     var removed = arr1.splice(3,2);
22     console.log(removed);    //输出：(2) [undefined, null]
23     console.log(arr1);        //输出：(3) ["a", "b", "c"]
24     //插入任意数量的项
25     //splice(起始位置，要删除的项数，要插入的项)
26     var inserted = arr1.splice(1,0,"insert");
27     console.log(inserted);   //输出：[]
28     console.log(arr1);         //输出：(4) ["a", "insert", "b", "c"]
29     var inserted2 = arr1.splice(1,2,"insert2");
30     console.log(inserted2);   //输出：(2) ["insert", "b"]
31     console.log(arr1);          //输出：(3) ["a", "insert2", "c"]
32     //向指定位置插入任意数量的项，同时删除任意数量的项
33     //splice(起始位置，要删除的项数，要插入的任意数量的项)
34     var instead = arr1.splice(1,2,"b");
35     console.log(instead);        //输出：(2) ["insert2", "c"]
36     console.log(arr1);            //输出：(2) ["a", "b"]
37 </script>