machinecat520
/
zj-Exercise


			
				
					
						
						
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							<!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>
    <!-- 
        1、依次输出什么？
        global begin:undefined
        foo()begin:1
        foo()begin:2
        foo()begin:3
        foo()end:3
        foo()end:2
        foo()end:1
        global end:1
        2、整个过程中产生了几个执行上下文?
            5个
     -->
    <script>
        console.log('global begin:' + i)
        var i = 1
        foo(1)
        function foo(i) {
            if (i == 4) {    //递归退出（终止）的条件
                return
            }
            console.log('foo()begin:' + i)
            foo(i + 1)   //递归调用：在函数内部调用自己
            console.log('foo()end:' + i)
        }
        console.log('global end:' + i)

        console.log('测试题1----------------------')

        //测试题1
        //先执行变量提升，再执行函数提升
        function a() { }
        var a
        console.log(typeof a)  //function

        console.log('测试题2------------------')

        //测试题2
        if (!(b in window)) {
            var b = 1
        }
        console.log(b)  //undefined

        console.log('测试题3------------------')

        //测试题3
        var c = 1
        function c(c) {
            console.log(c)
        }
        c(2)    //报错

        //测试题3
        var c = 1
        function c(c) {
            console.log(c)
            var c = 3
        }
        c(2)    //报错

    </script>
</body>

</html>