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Function declarations and variable declarations are always moved (“hoisted”) invisibly to the top of their containing scope by the JavaScript interpreter.
example1 :
var foo = 1; function bar() { if (!foo) { var foo = 10; } console.log(foo); // 10 } bar();
example2 :
var a = 1; function b() { a = 10; return; function a() { } } b(); console.log(a); // 1
example3 :
var x = 1; console.log(x); // 1 if (true) { var x = 2; console.log(x); // 2 } console.log(x); // 2
example4:
function foo() { var x = 1; if (x) { (function () { var x = 2; // some other code } ()); } // x is still 1. }
You can give names to functions defined in function expressions, with syntax like a function declaration. This does not make it a function declaration, and the name is not brought into scope, nor is the body hoisted. Here’s some code to illustrate what I mean:
example 5:
foo(); // TypeError "foo is not a function" bar(); // valid baz(); // TypeError "baz is not a function" spam(); // ReferenceError "spam is not defined" var foo = function () { }; // anonymous function expression (‘foo‘ gets hoisted) function bar() { }; // function declaration (‘bar‘ and the function body get hoisted) var baz = function spam() { }; // named function expression (only ‘baz‘ gets hoisted) foo(); // valid bar(); // valid baz(); // valid spam(); // ReferenceError "spam is not defined"
example 6:
getName(); //5 var getName = function () { console.log(4); }; function getName() { console.log(5); }; getName();//4
example 7:
function Foo() { getName = function () { console.log(1); }; return this; } Foo.getName = function () { console.log(2); }; Foo.prototype.getName = function () { console.log(3); }; var getName = function () { console.log(4); }; function getName() { console.log(5); }; Foo.getName(); //2 getName(); //4 Foo().getName(); //1 getName(); //1 new Foo.getName(); //2 new Foo().getName(); //3 new new Foo().getName(); //3
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原文地址：http://www.cnblogs.com/leonwang/p/5204441.html
