Edit in JSFiddle

function Person(name) {
    this.Name = name;
    this.sayHello = function () {
        alert('Hello there, I\'m ' + this.Name);
    };
}

function Student(name) {
    var that = new Person(name);
    that.codeWith = function (code) {
        alert(name + ' code with ' + code);
    };
    return that;
}
var mike = new Student('Mike');
mike.sayHello();
mike.codeWith('JS');