函數作用域如何在JavaScript中工作？

Question

JavaScript中的函數範圍如何工作？

Answer 1

// Create a new function = new scope 
(function() { 
    var a = 1; // create a new variable in this scope 

    if (true) { // create a new block 
     var a = 2; // create "new" variable with same name, 
        // thinking it is "local" to this block 
        // (which it isn't, because it's not a block scope) 
    } 

    alert(a); // yields 2 (with a block scope, a would still be 1) 
})(); 

alert(typeof a); // yields "undefined", because a is local to the function scope above 

試試：http://jsfiddle.net/9yr9U/