ES6-for...of与for...in

1.includes 数组是否包含某个东西

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

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>数组includes</title>
    <script>
        let arr = [12, 2, 99];
        alert(arr.includes(99));
    </script>
</head>

<body>

</body>

</html>

2.数组

2.1 keys/values/entries

keys=>所有的key拿出来 0,1,2,3.....
values=>所有的values拿出来 12,5,8,99.....
entries=>所有的key-value对拿出来 {key:0,value:12},{key:1,value:5},{key:2,value:8},{key:3,value:99}.....

2.2 for...of与for...in

操作	数组	json
for...in	下标(key)	json
for...of	值(value)	x

2.3 代码如下

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>数组for-in与for-of</title>
    <script>
        let arr = [12, 5, 8, 99];
        // 使用in，是循环出下标
        // for (let i in arr) {
        //     alert(i);
        // }
        // 使用of,是循环出当前值
        for (let i of arr) {
            alert(i);
        }
    </script>
</head>
<body>
</body>
</html>