js的隱式全局變量

function fn(){ a = 2; console.log(a); } fn();//執行後打印結果爲2 console.log(a)//不報錯，打印爲2 function fn(){ var a = b = c = 20; //隱式聲明瞭全局變量b,c         console.log(a);         console.log(b);         

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