学习ES6笔记-CFANZ编程社区

le目录

let

let

 <script>
        var song;
        let a;
        let b, c, d
        let e = 100;
        let f = 521, g = 'iloveyou', h = [];

        // 1,变量不重复声明
        let star = '易烊千玺';
        let star = '迪丽热巴'
        // 2,块级作用域  全局，函数，eval
        // if else while for
        {
            let girl = 'peiqi';
        }
        console.log(girl);
        //3, 不存在变量提升
        console.log(song);
        var song = 'yihihh';
        // 4,不影响作用域链
        {
            let school = 'sgg';
            function fn() {
                console.log(school);
            }
            fn();
        }
    </script>

let案例--修改颜色

let案例--修改颜色

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .item {
            width: 150px;
            height: 90px;
            border: 300px blueviolet;
            background: rgb(223, 126, 126);
            display: inline-block;
        }
        .page-header {
            background-color: pink;
        }
    </style>
</head>
<body>
    <div class="container">
        <h2 class="page-header">点击切换颜色</h2>
        <div class="item">1</div>
        <div class="item">2</div>
        <div class="item">3
        </div>
    </div>
    <script>
        let items = document.getElementsByClassName('item');
        // 遍历并绑定事件
        for (let i = 0; i < items.length; i++) {
            items[i].onclick = function () {
                // 修改当前元素的背景颜色
                // this.style.background ='pink';
                items[i].style.background = 'pink'
            }
        }
    </script>
</body>
</html>

const


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        const SCHOOL = 'sgg';
        // 1,一定要赋初始值
        const A;
        // 2，一般常量是用大写
        const a = 100;
        // 3，常量的值不能修改i
        SCHHOOL = 'ayguigu';
        // 4，块级作用域
        {
            const PLAYER = 'UZI'
        }
        console.log(PLAYER);
        // 5，对于数组和对象的元素修改，不算做对常量的修改，不会报错
        const TEAM = ['uzi', 'ming', 'mxlg', 'letme']
    </script>
</body>
</html>