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@@ -0,0 +1,47 @@
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+<!DOCTYPE html>
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+<html lang="en">
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+<head>
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+ <meta charset="UTF-8">
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+ <meta http-equiv="X-UA-Compatible" content="IE=edge">
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+ <meta name="viewport" content="width=device-width, initial-scale=1.0">
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+ <title>Document</title>
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+</head>
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+<body>
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+ <script>
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+ //创建一个变量 关键词是var
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+ var xx;
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+ //赋值
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+ xx = 99
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+ //输入变量的名称 在浏览器端查看这个变量的值
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+ console.log(xx)
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+ // console.log(XX)
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+
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+ /*
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+ 1.变量必须要以字母开头
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+ 2.变量可以包括字母、数字、下划线或者美元符号$
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+ 3.变量可以以_ $ 作为开头但是不建议这么做
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+ 4.变量对于大小写敏感
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+ */
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+
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+ // var a = '99' // string
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+
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+ var a = 111; //number 数字
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+ var B = 222;
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+ console.log(B)
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+ console.log(a)
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+
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+ var c = '我是小明 b,。dsuy%&*(%……#' //string 字符串
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+ console.log(c)
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+
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+ var d = true //boolean 布尔值 只有两个值 true false
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+ console.log(d)
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+
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+ var e ; //undefined
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+ console.log(e)
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+
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+ console.log(f)
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+
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+ //null
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+ </script>
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+</body>
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+</html>
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