Javascript String color(color)

String.prototype.color = function(color) {
 if(! color) color = 'green';
 
 var colors = {//www . j  a  v a  2  s. com
  black: 30,
  red: 31,
  green: 32,
  yellow: 33,
  blue: 34,
  white: 37
 }
 
 return "\033[" + colors[color.toLowerCase()] + "m" + this.toString() + "\033[0m";
}

/* Tweet version
String.prototype.color=function(c){l={black:30,red:31,green:32,yellow:33,blue:34,white:37};return"\033["+l[c]+"m"+this+"\033[0m"}
*/