263 扩展运算符...（展开语法）

扩展运算符可以将 数组 或者 对象 转为用逗号分隔的参数序列。

 let ary = [1, 2, 3];
 ...ary  // 1, 2, 3
 console.log(...ary);    // 1 2 3,相当于下面的代码
 console.log(1,2,3);

 let obj = {aa: 11, bb: 22, cc: 33}
 let obj2 = {dd: 44}
 console.log({...obj, ...obj2}) // {aa: 11, bb: 22, cc: 33, dd: 44}
扩展运算符可以应用于合并数组
 // 方法一 
 let ary1 = [1, 2, 3];
 let ary2 = [3, 4, 5];
 let ary3 = [...ary1, ...ary2];

 // 方法二 
 ary1.push(...ary2);
console.log(arr1);
将类 数组 或 可遍历对象 转换为 真正的数组
let oDivs = document.getElementsByTagName('div'); 
oDivs = [...oDivs];

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>扩展运算符</title>
</head>

<body>
    <div>1</div>
    <div>4</div>
    <div>3</div>
    <div>6</div>
    <div>2</div>
    <div>5</div>
    <script type="text/javascript">
        // 扩展运算符可以将数组拆分成以逗号分隔的参数序列
        let ary = ["a", "b", "c"];
        // ...ary; // "a", "b", "c"
        console.log(...ary); // a  b  c
        console.log("a", "b", "c"); //  a  b  c

        // 扩展运算符应用于数组合并
        let ary1 = [1, 2, 3];
        let ary2 = [4, 5, 6];
        // ...ary1 // 1, 2, 3
        // ...ary1 // 4, 5, 6
        let ary3 = [...ary1, ...ary2];
        console.log(ary3); // [1, 2, 3, 4, 5, 6]

        // 合并数组的第二种方法
        let ary11 = [1, 2, 3];
        let ary22 = [4, 5, 6];

        ary11.push(...ary22);
        console.log(ary11); // [1, 2, 3, 4, 5, 6]

        // 利用扩展运算符将伪数组转换为真正的数组
        var oDivs = document.getElementsByTagName('div');
        console.log(oDivs); // HTMLCollection(6) [div, div, div, div, div, div]
        var ary33 = [...oDivs];
        ary33.push('a');
        console.log(ary33); // [div, div, div, div, div, div, "a"]
    </script>
</body>

</html>

posted on 2020-01-27 20:57  冲啊！  阅读(168)  评论(0)  编辑  收藏  举报

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