js预编译和作用域
<script type="text/javascript"> var a = "hello"; b = "world"; Test(); function Test() { alert(a + " " + b); var a = "welcome"; b = "china"; alert(a + " " + b); } alert(a + " " + b); script>预编译后
<script type="text/javascript"> var a = "hello"; b = "world"; function Test() { var a = "undefined"; alert(a + " " + b); a = "welcome"; b = "china"; alert(a + " " + b); } Test(); alert(a + " " + b); script>
当我们写下：var i=1时，其实就是声明了一个window作用域的一个变量。
而当我们写下i=1时，是声明了一个window的属性。
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