The different between var == and ===

 == non-strict comparison operator

 //可以比较两个参数，即便是不同的类型
 Example:

 var a = "1";
 alert(a == 1); // true
 alert(a == "1"); //true

 === strict comparison operator
 
 //可以比较两个参数，但必须是相同的类型，否则返回false
 Example:

 var a = "1";
 alert(a === 1);// false;
 alert(a === "1");//true;

any more??????????????????????  

 but,Boolean with String is different situation.

 //不知作何解释，测试不行 == 与 === 结果是一样的
 var a = "true";
 alert(a ==/=== true);//false;
 alert(a ==/=== 1); //false;
 alert(a ==/=== "true");//true;
 
 //但是这样就行，JavaScript不能强制转换 Boolean类型
 var a = true;
 alert(a == "1");//true;
 alert(a === "1");//false;

 reference: http://stackoverflow.com/questions/523643/difference-between-and-in-javascript