js 중위 수 부족 자동 추가 확장 padLeft,padRight 구현 코드

function FillZero(p) {
return new Array(3 - (p + '').length + 1).join('0') + p;
}
FillZero(6); //  006

String.prototype.PadLeft = function (len, charStr) {
var s = this + '';
return new Array(len - s.length + 1).join(charStr || '') + s;
}
String.prototype.PadRight = function (len, charStr) {
var s = this + '';
return s + new Array(len - s.length + 1).join(charStr || '');
}
var p = 6;
p.toString().PadLeft(3, '0'); //  006
p.toString().PadRight(3, '0'); //  600

<script type="text/javascript">
String.prototype.pad= function (pos,len,padStr) {
 var padStrs = new Array(len).join(padStr,'');
 return pos ? (padStrs + this.toString()).substr(0-len):(this.toString() + padStrs).substr(0,len);
}
String.prototype.lpad = function(len,padStr){
	return this.pad(1,len,padStr);
}
String.prototype.rpad = function(len,padStr){
	return this.pad(0,len,padStr);
}
String.prototype.padLeft = String.prototype.lpad;
String.prototype.padRight = String.prototype.rpad;
var str="6";
console.log(str.lpad(2,"0"));
console.log(str.padLeft(2,"0"));
</script>

String.prototype.padLeft = function (padChar, width) {
 var ret = this;
 while (ret.length < width) {
  if (ret.length + padChar.length < width) {
   ret = padChar + ret;
  }
  else {
   ret = padChar.substring(0, width - ret.length) + ret;
  }
 }
 return ret;
};

String.prototype.padRight = function (padChar, width) {
 var ret = this;
 while (ret.length < width) {
  if (ret.length + padChar.length < width) {
   ret += padChar;
  }
  else {
   ret += padChar.substring(0, width - ret.length);
  }
 }
 return ret;
};

//cache
var padding1="00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000";
var padding2="                         ";
 function leftpad(str,length,useSpace){
 var padding = padding1;
 if(useSpace){
 padding = padding2;
 }
 
 
 var cnt = length-str.length;
 
 if(cnt<=0) return str;
 if(cnt<=200) return padding.substring(0,cnt)+str;
 
 
 str=padding+str; 
 return leftpad(str,length,ch); 
 }