Practical Object Orientation in JavaScript

http://www.phpied.com/3-ways-to-define-a-javascript-class/

methods defined internally

function Apple (type) {
    this.type = type;
    this.color = "red";
    this.getInfo = function() {
        return this.color + ' ' + this.type + ' apple';
    };
}

methods added to the prototype

function Apple (type) {
    this.type = type;
    this.color = "red";
}
 
Apple.prototype.getInfo = function() {
    return this.color + ' ' + this.type + ' apple';
};

using object literal syntax to create a singleton class

var apple = {
    type: "macintosh",
    color: "red",
    getInfo: function () {
        return this.color + ' ' + this.type + ' apple';
    }
}