JS Design Patterns

Some practical design patterns adapted to JS

Creational Patterns

Revealing Module Pattern

Wrap all functionality in a function and decide what will be public by returning it

Constructor Pattern

Create objects from functions

Factory Pattern

A pattern used to simplify object creation

Singleton Pattern

Used to restrict an object to only one instance to be shared across the application.

• The Singleton Remembers the last time you used it
• Hands the same instance back
• Node.js uses CommonJS

In Node Modules in Node CommonJS are cached after the first time they are loaded. Thi means that every call to require("foo") will get exactly the same object returned, if it would resolve to the same file.

If you want to have a module execute code multiple times, then export a function, and call that function. module.exports = myFunction();

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Structural Patterns

Concerned with how objects are made up and simplify relationships between objects.

• Deal with the relationship of objects
• Extend functionality
• Simplify functionality

Façade Pattern

Provide a simplified interface to a complicated system Example of facade pattern is jQuery simpifying the complicated DOM API

Decorator Pattern

Add new functionality to an existing object without being intrusive

Flyweight Pattern

Saves memory by sharing portions of an object between objects

• Only usable if you have large number of objects. Like a LOT. (> 1000000)

Sees if an object with a combination of property values was already created, and reuse that, don't create another one

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Behavioural Patterns

How objects relate to each other

Mediator pattern

Controls communication between objects so neither object has to be coupled to the others.

Observer pattern

Loosely coupled system