javascript练习-私有状态

function Range(from, to){
  this.from = function(){return from;}
  this.to = function(){return to;}
}

Range.prototype = {
  constructor: Range,
  includes:function(x){return this.from() <= x && x <= this.to();},
  foreach:function(f){
    for(var x = Math.ceil(this.from()),max = this.to();x < max;x++)f(x);
  },
  toString:function(){
    return "(" + this.from() + "..." + this.to() + ")";
  }
}