Javascript Type-Conversion_parseInt

参考资料：http://jibbering.com/faq/notes/type-conversion/

console.log(String(null));
console.log(String(null)=='null');//true
console.log(parseInt(''));//NaN
console.log(Number(''));//0
console.log(parseInt(null));//NaN
console.log(Number(null));//0
console.log(parseInt(undefined));//NaN
console.log(Number(undefined));//NaN
console.log(parseInt("123rrr"));//123
console.log(Number("123rrr"));//NaN
function a(){}
a.prototype.valueOf=function(){return 2;}
a.prototype.toString=function(){return 3;}
var b=new a();
console.log(b==2);//true
console.log(Number(b)==2);//true
console.log(parseInt(b));//3
console.log(parseInt(b)==2);//false
console.log(parseInt(b)==3);//true

parseint转换Object对象时，是调用的对象的方法toString，