很有意思的JS

 每段放一起和分開執行結果是不一樣的

 

 

今天看到有5道Javascript題目，很有意思，值得琢磨。原文爲zaka在twitter發的回答Baranovskiy的So, you think you know JavaScript。原文如下：
Quick test for real understanding of JavaScript core beyond closures and scopes. Here five small scripts. Try to answer what will be alerted in each case without running them in the console. Then you could create a test file and easily check your answers. Ready?

 

if (!("a" in window)) { var a = 1; } alert(a); var a = 1, b = function a(x) { x && a(--x); }; alert(a); function a(x) { return x * 2; } var a; alert(a); function b(x, y, a) { arguments[2] = 10; alert(a); } b(1, 2, 3); function a() { alert(this); } a.call(null);

大家想想看吧

先不要偷看結果:
undefined
1
function a(x){
return x * 2;
}
10
[object]

 

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