Constructor function example

gistfile1.js

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

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

var r = new Range(1, 3);
r.includes(2);
r.foreach(console.log);
console.log(r);