function w(s){ document.writeln("<br/>"); document.writeln(s); document.writeln("<br/>-----------------------------"); } String.prototype.valueOf=function(){return 1;}; w(+new String("sss"));//输出1 String.prototype.valueOf=function(){return "a";}; w(+new String("sss"));//输出NaN Date.prototype.valueOf=function(){return 1;}; w(+new Date());//输出1 Date.prototype.valueOf=function(){return "a";}; w(+new Date());//输出NaN Object.prototype.valueOf=function(){return 1;}; w(+{});//输出1 Object.prototype.valueOf=function(){return "a";}; w(+{});//输出NaN Array.prototype.valueOf=function(){return 1;}; w(+[]);//输出1 Array.prototype.valueOf=function(){return "a";}; w(+[]);//输出NaN var s=function(){}; Function.prototype.valueOf=function(){return 1;}; w(+s);//输出1 Function.prototype.valueOf=function(){return "a";}; w(+s);//输出NaN Boolean.prototype.valueOf=function(){return 1;}; w(+new Boolean());//输出1 Boolean.prototype.valueOf=function(){return "a";}; w(+new Boolean());//输出NaN

w(+5);//输出5 w(+true);//输出1 w(+false);//输出0 w(+"ss");//输出NaN w(+"111");//输出111