如何将阿拉伯数字每三位一逗号分隔，如：15000000转化为15,000,000

"15000000".split("").reverse().join("").replace(/(\d{3})/g, "$1,").split("").reverse().join("");

"115000000".split("").reverse().join("").replace(/(\d{3})(?=[^$])/g, "$1,").split("").reverse().join("");

var cutStr = function(str)
{
  var newStr= new Array(str.length+ parseInt(str.length/3)); 
  newStr[newStr.length-1]=str[str.length-1]; 
  var currentIndex=str.length-1; 
  for(var i = newStr.length-1;i >= 0;i--) 
  { 
    if((newStr.length-i)%4==0) 
    { 
      newStr[i]=","; 
    }
    else
    { 
      newStr[i]=str[currentIndex--]; 
    } 
  } 
  return newStr.join("") 
} 
var num="15000000";
console.log(cutStr(num));

function cutStr(str){
    var rmb='';
    var i2=0;
    for(var i=str.length-1; i>=0; i--){

        if(i%3==0&&i!=0){
            rmb+=str[i2]+',';
        }else{
            rmb+=str[i2];
        }
        i2++;
    }
    return rmb;
}
console.log(cutStr(num));

function cutStr(num) {
    var aaa = num.toString();
    var arr1 = aaa.split("");
    var arr2 = [];
    for (var i = 0; i 

'1500000000000'.replace(/\B(?=(\d{3})+$)/g,',')




function formatNumber(value) {
    value = value.toString();
    if (value.length 

var str = '123123211312.333123'.replace(/(?=(?!^)(?:\d{3})+(?:\.|$))(\d{3}(\.\d+$)?)/g,',$1');
console.log(str)