JavaScript design pattern: difference between module pattern and revealing module pattern?

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It also makes it easier to tell at the end of the module which of our functions and variables may be accessed publicly, which eases readability. We are storing returned public methods in namesCollection variable. Now you can call namesCollection.addObject() method, which is a public method. But can not call printMessage method because this is not exposed in return. To modify this to match the Revealing Module pattern, I moved everything into private methods and created a much simpler return block.

  • All references are via the closure variables, not the return object.
  • What this does is instantiate a new Object, and bind our extension method to it, and return it.
  • If you want to make name and sayHello private as before, the references to the now-private members have to be changed.
  • Unless otherwise noted, all code is free to use under the MIT License.
  • ( I prefer to think of simple patterns as design conventions.) I’m way far from being a JavaScript expert yet.

It also allows the developer to avoid a lot of `this.` in the code. Functions that should be exposed publicly are defined in the return section of the calculator object. In this example the init, numberClick, setOperator and clearNumbers Remote ASP NET MVC Developer Jobs in 2022 functions are exposed by simply defining a JavaScript object literal that is returned when the main calculator function is invoked. All of the other functions and variables defined in the calculator object are private.

Keep in mind that each call to Calculator() places a new copy of each function in memory, but the impact is quite minimal in this case. If you’re worried about multiple copies of functions being placed in memory as objects are created then consider using the Revealing Prototype Pattern since it leverages JavaScript prototyping. It declares a function, which then calls itself immediately.

Design patterns prove crucial to solving this challenge – providing an organization structure for common issues in a particular circumstance. Although this looks much cleaner, an obvious disadvantage is unable to reference the private methods. Similarly, the public behaviors are non-overridable. But the issue with Object Literals is the pattern can be abused. Methods intended to be “private” will be accessible by users because they are part of the Object. This is where the Module comes in to save us, by allowing us to define all our “private” stuff locally and only return “the good parts”.

Anonymous closures are just functions that wrap our code and create an enclosed scope around it. Closures help keep any state or privacy within that function. Closures are one of the best and most powerful features of JavaScript.

When I call myModule.testpub, the public interface, it is connected to the functions that were defined privately. I have recently been getting into the habit of leveraging the revealing module pattern for all my code. I used this guide for inspiration, but my code doesn’t feel as elegant.

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I’ll be watching so I learn something about that too. If it sounds like the Revealing Module is just a cosmetic change, that would be fair I think. Anything that makes you quicker, more efficient, etc in your development is probably a good thing. I’d also argue that the issue with “public calling public” is something you could easily accidentally trip into.

John, the fact that b has to prefix module to the call is part of the problem though. By moving to the revealing module pattern, all my functions can access each other ‘naked’. It isn’t that it isn’t fixable, my second code sample shows that fix, it is more a, “If you prefer to use modules and want to not worry about it, consider this version.” It has been a few weeks since my last blog post on JavaScript design patterns. I’d apologize, but frankly, it will probably be a few more weeks until I blog on this subject again, so hopefully people aren’t expecting a fast series here .

revealing module pattern

Some challenges include additional information to help you out. Enter your email address to follow this blog and receive notifications of new posts by email. Join 2,458+ other developers and get free, weekly updates and code insights directly to your inbox. Let’s consider the following example where we create the object clarkKent. If you want to make name and sayHello private as before, the references to the now-private members have to be changed. Using our old example, you can see that public members are directly added to the stub object.

We then have Module declared in the global scope, which means we can call it wherever we like, and even pass it into another Module. Note that unlike RMP, in order to make name and sayHello private, the references pointing to name and sayHello in the various function body definitions also have to be changed. To make this guide a bit more tangible, we’re going to build a few different libraries around a set of helper functions that perform basic math. Get Mark Richards’s Software Architecture Patterns ebook to better understand how to design components—and how they should interact. As you can see your code has become more readable now, since your event bindings are at top and their respective functions are at bottom.

The Module Pattern with Return Object Stub

We get the benefits of the module container, an easier to read api, and the ability to new up as many instances as we like. Note that in the object literal, the name of they key of each key/value pair, is the name of the exposed member. In our example here we simply returned a one to one mapping of alias to name for the public members. If you wanted to name your function one thing on the inside of the module, and expose it publicly as another name to external callers, you can do that as well. In our example we have a gofast() function and that is how we call it on our instances. What if you wanted to have people call that function using blastoff instead of gofast?

Lexical scope of JavaScript functions keeps data that shouldn’t be accessible by the user private . Immediately Invoked Function Expression (or IIFE, pronounced “iffy”) exports only public-facing API and assigns it to the myModule variable. Before ECMAScript 2015, JavaScript language was lacking an official module system. Lack of namespacing and protecting against polluting the global environment forced developers to design many solutions for this problem. Just try to do something based on top comment answer.

Learning JavaScript Design Patterns by Addy Osmani

The above example declares our function privateMethod, which is locally declared inside the new scope. If we were to attempt calling it anywhere outside of our module, we’ll get an error thrown and our JavaScript program will break! We don’t want anyone to be able to call our methods, especially ones that might manipulate data and go back and forth to a server.

I’m a massive fan of JavaScript’s Module Pattern and I’d like to share some use cases and differences in the pattern, and why they’re important. The Module Pattern is what we’d call a “design pattern,”and it’s extremely useful for a vast amount of reasons. My main attraction to the Module Pattern is it makes scoping a breeze and doesn’t overcomplicate program design. Encapsulation, or information hiding in other words, is one of the core characteristics of every module system. A well-designed module should export only a simple interface and keep the irrelevant logic private and inaccessible. All references are via the closure variables, not the return object.

revealing module pattern

The Module Pattern is not a silver bullet for adding code re-usability to your JavaScript. Using the Module Pattern with Prototypal Inheritance or ES6 Classes can give you a wide range of design patterns with varying pros How to Become a Programmer: A Step-By-Step Guide for 2022 and cons. JavaScript does not have a private keyword by default but using closures we can create private methods and private state. Following this technique, multiple objects can be created as needed in a page or script.

This is a very clean way of specifying the public members and functions that you want to define to the outside world. The biggest advantage of revealing module pattern as compared to the module pattern is the code readability aspect. Usually, object-oriented languages such as Java provide ‘private’, ‘protected’, and ‘public’ access modifiers which help us to protect the variables and functions/methods using the keyword ‘private’. To create a revealing module pattern, you assign an immediately invoked function expression to a variable. Let’s first see how Javascript’s function-level scope can help us create public and private methods. This pattern allows the syntax of our scripts to be more consistent.

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The return block is now far simpler – it just provides the public API. JavaScript modules are the most prevalently used design patterns for keeping particular pieces of code independent of other components. This provides loose coupling to support well-structured code. One of my favorite overall JavaScript patterns is the Revealing Module Pattern since it’s cleaner with less usage of the “this” keyword.

  • For example, the previous code uses myCalc to call the Calculator object’s init() function.
  • Public object members which refer to private variables are also subject to the no-patch rule notes above.
  • But can not call printMessage method because this is not exposed in return.
  • Notice that callChangeHTML binds to the returned object and can be referenced within the HTMLChanger namespace.
  • I don’t care where the data came from so long as it equals my mock data and ‘whatever’ is set properly.

For example, I have a FormManager module that creates a form-specific object to manage every aspect of a form’s data, including custom validation and caching. I can create as many form-manager instances as needed without worrying about ‘bleed’ from one instance to another. Now we can access all the methods that we need on our musicModule object.

Understanding “return”

Thank’s Raymond you have explained it very nicely,the part you are talking silly that helped me to understand why we need I don’t see how you can say, “I don’t care where the data came from so long as it equals my mock data and ‘whatever’ is set properly.”, and the say you check to see if a particular service is run. If your intent is to ensure getData works online or offline, and you mock that status, then you expect data in both cases. You would test for getting data back, now how it got it.

To be fair, the revealing module pattern is very similar to the module pattern, but it has a really nice way of exposing the api of a module to it’s users or consumers. I think you’ll find the revealing module pattern to be a really good balance of how to structure your JavaScript code for readability. The Module Pattern is one of the most common design patterns used in JavaScript and for good reason.