lovecoding
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 变量声明 赋值 
        var a = 1;
        let b = 2;
        console.log(b);
        /**
         * var 与 let 区别
         * 1.var 具备变量提升，let不具备变量提升
         * 2.let 不能重复声明
         * 3.临时失效区 在同一区域内 不能使用let进行同命名
        */
        // 变量提升    
       console.log(a1);
        //console.log(b1);
       var a1;
       let b1 = 0;
       var a = 6;
       console.log(a);
       let b2 = 12;
       function fn() {
        // var c = 3;
       }
       fn();
    //    console.log(c);

    var a2 = '2222';
       function fn2() {
        var a2 = '111';
        console.log(a2); // 111
       }
       fn2();
       console.log(a2); // 2222

       let a3 = '2222';
       function fn2() {
        let a3 = '111';
        // let a3 = '2222'
        console.log(a3);
       }
       fn2();
       console.log(a3);
    </script>
</body>
</html>