Understanding the Prototype Design Pattern in JavaScript

The "Prototype Design Pattern" in JavaScript allows for creating clones of objects that can be used in different parts of an application without the need to repeat the expensive creation process each time. We'll walk you through the basics.

The Prototype Design Pattern is an important concept in JavaScript that is based on the principle of prototypical inheritance. Many JavaScript developers have encountered the "prototype" keyword, puzzled over prototypical inheritance, or implemented prototypes in their code. This pattern leverages the JavaScript prototype model to create objects in performance-intensive situations.

The created objects are clones (shallow clones) of the original object that can be passed around. One use case of the Prototype pattern is to avoid costly database operations for creating an object for other parts of the application. Instead of repeating the same costly operation, it can be advantageous to clone a previously created object.

Using the Prototype Pattern

To clone an object, a constructor must be present to instantiate the initial object. Subsequently, variables and methods are bound to the object's structure using the "prototype" keyword. Here is a simple example:

var TeslaModelS = function() {
    this.numWheels    = 4;
    this.manufacturer = 'Tesla';
    this.make         = 'Model S';
}

TeslaModelS.prototype.go = function() {
    // Turn wheels
}

TeslaModelS.prototype.stop = function() {
    // Apply brake pads
}

The constructor allows for creating a single TeslaModelS object. When a new TeslaModelS object is created, it retains the states initialized in the constructor. Adding functions like "go" and "stop" is straightforward since we declared them using "prototype."

An alternative method for extending functions within the prototype is as follows:

var TeslaModelS = function() {
    this.numWheels    = 4;
    this.manufacturer = 'Tesla';
    this.make         = 'Model S';
}

TeslaModelS.prototype = {
    go: function() {
    // Turn wheels
    },
    stop: function() {
    // Apply brake pads
    }
}

The Revealing Prototype Pattern

Similar to the module pattern, there is also a variant of the Prototype pattern known as the "Revealing Prototype Pattern." This variant allows for encapsulating public and private members by returning an object literal.

By returning an object, the prototype object name is associated with a function, enabling control over what should be exposed in the current prototype to manage access:

var TeslaModelS = function() {
    this.numWheels    = 4;
    this.manufacturer = 'Tesla';
    this.make         = 'Model S';
}

TeslaModelS.prototype = function() {

    var go = function() {
    // Turn wheels
    };

    var stop = function() {
    // Apply brake pads
    };

    return {
    pressBrakePedal: stop,
    pressGasPedal: go
    }

}();

Note that the "stop" and "go" functions are encapsulated before the returned object because they are outside the scope of the returned object. Since JavaScript natively supports prototypal inheritance, there's no need to rewrite fundamental functions.

The Prototype Design Pattern is a powerful concept that enables efficient object creation in JavaScript and facilitates object reuse in complex applications. Understanding the Prototype Design Pattern