lovecoding
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VIP28


			
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<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 和 var的区别
    1.const 不能重复赋值
    2.const 不能重复声明
    3.const 没有变量提升
    4.const 具有块级作用域
    5.const 临时失效区
    */
    // const a = 100
    // a = 200
    // console.log(a)


    // const a = 100
    // const a = 200
    // console.log(a)

    // console.log(a)
    // const a = 100

    // const a = 100
    // function fn(){
    //   a = 10
    //   console.log(a)
    // }
    // fn()

    // var a = true
    // if(a){
    //   const x = 100
    // }
    // console.log(x)


    var a = true
    if(a){
      var b = 10
      let x = 100
    }
    b = 30
    x = 10
    const c = 200
    function fn(){
      console.log(b)
      // console.log(h)
      // console.log(xx)
      let xx = 30
      var b = 300
      const x = 30
      console.log(x)
      console.log(c)
    }
    fn()
    console.log(a,b,x,c)

    // undefined 报错  30 200   true,30,报错,200
    // undefined 报错  10 200   true,30,报错,200
    // undefined 报错  30 200   true,30,10,200
    // undefined 报错  30 200   true,300,报错,200

  </script>
</body>
</html>