js重修课[五]：类与模块

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

Range.prototype.includes = function(x) {
    return this.form <= x && x <= this.to;
};

Range.prototype.foreach = function(f) {
    for (var x = Math.ceil(this.from); x <= this.to; x++)
      f(x);
};

Range.prototype.toString = function() {
    return "(" + this.from + "..." + this.to + ")";
};

Range.ZERO = new Range(0, 0);