http://blog.ashworth.in/introduction-to-advanced-javascript-prototyping/

gistfile1.js

// This is the constructor
function Client(name, age) {
    this.name = name;
    this.age = age;
}

Client.prototype.contact = function() {
    console.log("Now contacting " + this.name + "...");
}

var myClient = new Client('Test Client', 21);
myClient.contact();