变量提升

变量声明提升 Vs. 函数声明提升 1. 变量声明提升       先看以下代码： 1）var in_window = "a" in window; console.log(in_window);  2）var in_window = "a" in window; console.log(in_window); if(!("a" in window)) { var a = 1; } 3）var a

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