javascript: 数字の桁揃え

format_decimal.js

// repeat character
String.prototype.repeat = function(num) {
  return new Array(num + 1).join(this); 
}
// convert strings and filling zero
String.prototype.decimalf = function(num) {
  if (isNaN(this) || isNaN(num) || num < 0){ return this;};
  ary = this.split(".");
  if(num == 0) { return ary[0]; };
  ary[1] = (((ary.length>2)? ary[1] : "") + "0".repeat(num)).substring(0,num);
  return ary.slice(0,2).join(".");
}