关于javascript:js中的加号运算符

一,对于援用类型对象(我指的是String,Date,Object,Array,Function,Boolean)的+运算符运算过程如下! 1,首先调用此对象的valueOf办法,失去返回数值A 2,而后把此数值A转换成数字,失去的是最终数值 function w(s){ document.writeln("<br/>"); document.writeln(s); document.writeln("<br/>-----------------------------"); } String.prototype.valueOf=function(){return 1;}; w(+new String("sss"));//输入1 String.prototype.valueOf=function(){return "a";}; w(+new String("sss"));//输入NaN   Date.prototype.valueOf=function(){return 1;}; w(+new Date());//输入1 Date.prototype.valueOf=function(){return "a";}; w(+new Date());//输入NaN  Object.prototype.valueOf=function(){return 1;}; w(+{});//输入1 Object.prototype.valueOf=function(){return "a";}; w(+{});//输入NaN  Array.prototype.valueOf=function(){return 1;}; w(+[]);//输入1 Array.prototype.valueOf=function(){return "a";}; w(+[]);//输入NaN  var s=function(){}; Function.prototype.valueOf=function(){return 1;}; w(+s);//输入1 Function.prototype.valueOf=function(){return "a";}; w(+s);//输入NaN  Boolean.prototype.valueOf=function(){return 1;}; w(+new Boolean());//输入1 Boolean.prototype.valueOf=function(){return "a";}; w(+new Boolean());//输入NaN 

二,对于根本数据数据类型,其值转换成数字w(+5);//输入5 w(+true);//输入1 w(+false);//输入0 w(+"ss");//输入NaN w(+"111");//输入111