Скачать или смотреть JavaScript Prototypal Inheritance: Hoozit.prototype=new Gizmo() & Hoozit.prototype = Gizmo.prototype

Dive into JavaScript's prototypal inheritance and learn why using `Hoozit.prototype = new Gizmo()` is different from `Hoozit.prototype = Gizmo.prototype`.
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JavaScript Prototypal Inheritance: Hoozit.prototype=new Gizmo() & Hoozit.prototype = Gizmo.prototype

JavaScript is a powerful language that allows for flexible object-oriented programming through a mechanism known as prototypal inheritance. When it comes to implementing inheritance in JavaScript, there are multiple ways to achieve it. A key distinction lies in how one sets up the prototype chain between a child and a parent object. This post will focus on comparing two common patterns: Hoozit.prototype = new Gizmo() and Hoozit.prototype = Gizmo.prototype.

What is Prototypal Inheritance?

Prototypal inheritance allows objects to inherit properties and methods from other objects. In JavaScript, this is typically done by setting an object’s prototype property to another object's prototype. This way, the child object can access the parent’s properties and methods via the prototype chain.

The new Gizmo() Approach

When you see Hoozit.prototype = new Gizmo(), it means you're creating a new instance of Gizmo and assigning it as the prototype of Hoozit. This newly created instance will serve as a prototype for all instances of Hoozit.

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Pros:

Isolation: Changes to Gizmo.prototype won’t affect Hoozit.prototype, preserving Hoozit's independent methods and properties.

Instance Properties: Ensures that any property defined directly on new Gizmo() is available to instances of Hoozit.

Cons:

Resource Intensive: Creating an instance (using new) for assigning the prototype can consume more memory, especially if Gizmo's constructor does a lot of work or has many properties.

The Gizmo.prototype Approach

When using Hoozit.prototype = Gizmo.prototype, you're pointing the prototype of Hoozit directly to Gizmo.prototype. Essentially, Hoozit and Gizmo will share the same prototype object.

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Pros:

Memory Efficiency: Since no new instance is created, you save memory and computational resources.

Simpler: Simpler inheritance model if you don't need to retain separate prototypes.

Cons:

Shared Prototype: Modifications to Gizmo.prototype will also affect Hoozit.prototype and vice versa, often leading to unexpected behaviors and bugs.

Loss of Independence: Any change to the prototype properties or methods is reflected in all objects sharing that prototype.

Which One to Use?

Choosing between Hoozit.prototype = new Gizmo() and Hoozit.prototype = Gizmo.prototype depends on your specific needs:

Use Hoozit.prototype = new Gizmo() if you want Hoozit to have an independent prototype and encapsulate properties from the parent object.

Use Hoozit.prototype = Gizmo.prototype if you want to save memory and share the prototype between Hoozit and Gizmo, but be cautious of the side effects.

Understanding these key differences is crucial for effective JavaScript programming, especially when dealing with complex inheritance hierarchies.