JavaScript Scoping and Hoisting

Do you know what value will be alerted if the following is executed as a JavaScript program? var foo = 1; function bar() { if (!foo) { var foo = 10; } alert(foo); } bar(); If it surprises you that the answer is “10”, then this one will probably really throw you for a loop: var a = 1; function b() { a = 10; return; function a() {} } b(); alert(a); Here, of course, the browser will alert “1”. So wha

[mooz]

JavaScript の Hoisting (持ち上げ) について. 変数と関数で名前が被った場合にどう扱われるかなど. var foo でパース時に foo を undefined で上書きしちゃうよ.