js的隐式全局变量

function fn(){ a = 2; console.log(a); } fn();//执行后打印结果为2 console.log(a)//不报错，打印为2 function fn(){ var a = b = c = 20; //隐式声明了全局变量b,c         console.log(a);         console.log(b);         

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