The Javascript regular expression implementation adds a thousand separator for a number

Recently, I saw an interview (written test) question that used js to realize the thousands separator of Numbers on the Internet, so I wrote a method to realize it by using "regular +replace" :

 var thousandBitSeparator = function(numStr){

     var b = /([-+]?\d{3})(?=\d)/g;

     return numStr.replace(b, function($0, $1){

         return $1 + ',';

     });

 }

Support plus and minus sign matching, decimal point differentiation, if there is an error, we hope to point out: -D

Attached is an implementation method of other netizens

<script language="JavaScript" type="text/javascript">  

function formatNumber(num){  

 if(!/^(\+|-)?(\d+)(\.\d+)?$/.test(num)){  

  return num;  

 }  

 var a = RegExp.$1,b = RegExp.$2,c = RegExp.$3;  

 var re = new RegExp().compile("(\\d)(\\d{3})(,|$)");  

 while(re.test(b)){  

  b = b.replace(re,"$1,$2$3");  

 }  

 return a +""+ b +""+ c;  

}  

var num=1234567/3;  

alert("num="+num+" . 4 Give up 5 In: "+Math.round(num)+" , two significant digits: "+num.toFixed(2)+" , add the thousands separator: "+formatNumber(num));  

</script>  

That's all for this article, I hope you enjoy it.