阅读这个你不知道 JS的作用域和闭包部分,它解释得很好尝试这个:function x () { a = 1; function foo() { /* when you write a = 2, you are assining 2 to the global a */ var a = 2; console.log("global a", window.a); console.log("local a", a); } foo();}; x();console.log(window.a);