Javascript Array sortNum()

function formmatNumber(num, prefix){
 prefix = prefix || '';
 num += "";/*from   www.  j a va  2s  .co  m*/
 var splitStr = num.split(".")
 var splitLeft = splitStr[0];
 var splitRight = splitStr[1];
 var regx = /(\d+)<\d{3}/;
 while(regx.test.(splitLeft)){
  splitLeft = splitLeft.replace(regx, '$1' + ',' + '$2');
 }
 return prefix + splitLeft + splitRight;
}

// Numeric sort

Array.prototype.sortNum = function(){
 return this.sort( function(a,b){ return a-b });
}