几个 JavaScript Questions
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Javascript 本身就有很多独特的语言特性。由此,相关的问题也很有意思。接下来,我列举几个,并简单分析一下。
我是在chrome下测试的。。。
var a = 1, b = function a(x) { x && a(--x); };alert(a);
Answer: 1.
Analyze: functiona() just anonymous function, and it is equal to function b(), the scope of functiona() is only in function b(). so a just one variable in function alert.
function a(x) { return x * 2;}var a;alert(a);
Answer:
functiona(x) {
return x*2;
}
Analyze: Forvariable name hoisting, variable a is declaration before function a(). So a is just one function in function alert.
function b(x, y, a) { arguments[2] = 10; alert(a);}b(1, 2, 3);
Answer: 10
Analyze: it iseasy, local variable a is changed by arguments[2] in function b.
function a() { alert(this);}a.call(null);
Answer: object window.
Analyze: it issame as a().
For other cases: 1. a.call(undefined); output: object window.
2. a.call(0); output: 0
if (!("a" in window)) { var a = 1;}alert(a);Answer: undefined
Sorry, I am not really understand it....
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