typeof用以获取一个变量的类型，typeof一般只能返回如下几个结果：number,boolean,string,function,object,undefined
instanceof用于判断一个变量是否某个对象的实例
Use instanceof for custom types:
1 var ClassFirst = function () {}; 2 var ClassSecond = function () {}; 3 var instance = new ClassFirst(); 4 typeof instance; // object 5 typeof instance == ‘ClassFirst‘; //obviously this one is false 6 instance instanceof Object; //true 7 instance instanceof ClassFirst; //true 8 instance instanceof ClassSecond; //false
Use typeof for simple built in types:
1 ‘example string‘ instanceof String; // false 2 typeof ‘example string‘ == ‘string‘; //true 3 ‘example string‘ instanceof Object; //false 4 typeof ‘example string‘ == ‘object‘; //false 5 true instanceof Boolean; // false 6 typeof true == ‘boolean‘; //true 7 true instanceof Object; // false 8 99.99 instanceof Number; // false 9 typeof 99.99 == ‘number‘; //true 10 function() {} instanceof Function; //true 11 typeof function() {}; //function
Use instanceof for complex built in types:
/regularexpression/ instanceof RegExp; // true typeof /regularexpression/; //object [] instanceof Array; // true typeof []; //object {} instanceof Object; // true typeof {}; //object
And the last one is a little bit tricki:
typeof null; //object
原文：http://www.cnblogs.com/kite-Runner/p/3529907.html