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The Revealing Module pattern can easily imitate either the Class Pattern or the Namespace Pattern with the added advantage of private state and private functions. This is most helpful in Scoped Applications where the app developer may prefer to keep implementation details hidden while exposing clear public interfaces. But it can also be used to help maintain clear API boundaries over time where traditional Javascript classes and objects would tend towards bloat. If you look at the return statement, the values of variables and functions can be returned in a conventional JavaScript way. We are using the addProperty, removeProperty, and displayPerson as pointers to the private functions.
- If you want to make name and sayHello private as before, the references to the now-private members have to be changed.
- 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.
- That object literal is exposing it’s api, or it’s methods, by defining their structure right inside that very object literal that is being returned.
- Since the function ‘callAddPropertyFn’ is inside the IIFE, it has access to all private variables and functions.
- With that one small change, you can now call code such as model3.blastoff() and roadster.blastoff(), and behind the scenes, it is actually the gofast() function providing the implementation for you.
If you want to make name and sayHello private as before, the references to the now-private members have to be changed. References to public members are via this, whenever possible. By resolving the ambiguity differently, you get variants of the Module Pattern. You can invoke the function ‘callAddPrpertyFn’ from outside the IIFE function as shown below. We will first create an IIFE and assign it to the constant module.
Now that we have the fundamentals of IIFE in place, let us look take a step-by-step approach to create a module pattern. Modules are an important piece of every modern application. They help us to organize and structure our codebase in a better way.
This little outline we have above is an example structure of the revealing module pattern. At first glance, it does indeed look quite similar to the module pattern that we already had a look at. This is not an actual requirement, but it is a good idea from a conventions standpoint, as it gives an indication that the new keyword is not required with the revealing module pattern. The reason no new keyword is required is because of those two little parenthesis after the function declaration. The biggest difference between the module pattern and the revealing module pattern however is in fact in the return statement.
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The code sample you showed is more of a mixin pattern to me, so it’s more flexible than the original module pattern, but both require the same understanding to execute correctly. If you pose an actual stackoverflow question, I can give a more detailed answer. In the following example, you can see how, in contrast to RMP, the function definitions are actually in the return object literal, and references to members are qualified by this. All references are via the closure variables, not the return object. If you console.log, then you’ll get ‘undefined’ since nothing is returned by this function. The IIFE contains a private ‘person’ object and a private function ‘addProperty’ that accepts a property name and a property value.
Describe the Revealing Module Pattern in JavaScript
What if we could combine this pattern with the Prototype Pattern though to get the benefits provided by prototyping? As a quick review, I showed the following code in the first post since it shows “function spaghetti code” and illustrates code that can be encapsulated into a more re-useable object. The code simply lists all functions directly with no encapsulation and defines several global variables. While the code works fine this way, I’ll examine how we can restructure it to follow the Revealing Module Pattern. Lexical scope of JavaScript functions keeps data that shouldn’t be accessible by the user private .
We can access and pass each property of the response object to a new variable. Design patterns allow developers to communicate better by providing a proper way of testing, implementing and maintaining code. Many design patterns can be used to help developers write better code. A disadvantage of this pattern is that if a private function refers to a public function, that public function canât be overridden if a patch is necessary. This is because the private function will continue to refer to the private implementation, and the pattern doesnât apply to public members, only to functions.
There are three main categories of design patterns—creational, structural and behavioral. Each category has many different design patterns that can be used to solve a specific problem. At the end of your code, you return an object with any of the functions that you want to make publicly available. The revealing module pattern is typically used for helper or utility libraries, collections of utility or helper methods . Let’s imagine we have a music application where a musicPlayer.js file handles much of our user’s experience.
When we’re writing code, breaking our code into small and manageable modules makes a difference in how our application is going to scale. As developers, we’re always striving to write clean and readable code. While solving many problems using technology, writing clean code is a must-do for every developer because it can save tons of resources, time and money in the future. As shown in the above pictorial representation , several methods combined together makes a big function functionality working .
Recall that in the module pattern, we defined our public functions right in the returned object literal. With the revealing module pattern, there is no need to do this! Let’s go ahead and refactor one of our prior examples to make use of the revealing module pattern. Functions that should be exposed publicly are defined in the return section of the Calculator object. All of the other functions and variables defined in the Calculator object are private.
The revealing module pattern is really almost the same as the module pattern. The major difference to be aware of is simply how the revealing module pattern exposes it’s api. In other words, what is contained in the return statement of the revealing module pattern is different than what is in the module pattern. Just like we saw with the module pattern, the revealing module pattern also allows developers to emulate the concepts of public and private variables and functions.
What does the revealing module pattern provide us?
Now that we have a good understanding of closure, the prototype pattern, and the module pattern, let us now take a look at the JavaScript Revealing Module Pattern. You know it’s funny, we have all this verbiage to describe these patterns, and you might be scratching your head as to what a module pattern vs a revealing module pattern is. 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 a design pattern used for improving the maintainability and reusability of the code by creating public and private access levels.
Immediately Invoked Function Expression (or IIFE, pronounced “iffy”) exports only public-facing API and assigns it to the myModule variable. While the code works fine this way, I’ll examine how we can restructure it to follow the Revealing Module Pattern. The revealing module pattern is used to provide an abstraction over private implementations by providing public APIs. Since the function ‘callAddPropertyFn’ is inside the IIFE, it has access to all private variables and functions. We return a public method ‘callAddPropertyFn’ from the IIFE.
JavaScript doesn’t support accessibility modifiers as C# or Java do but this pattern provides a nice way to emulate that type of functionality. The Revealing Module Pattern builds on the traditional module pattern by selectively exposing the private methods and variables of a module. Instead of returning an object literal that contains all of the public methods and variables, we define the public methods and variables as properties of the module’s returned object. This allows us to keep the private methods and variables hidden, while still providing a way to access them.
With the revealing module pattern, you can define your variables and methods right up in the area we normally consider private . Then, you still return an object, but that object will have simple key/value pair references to anything you want to make public to a consumer of the module. In JavaScript, a module is typically created using an immediately-invoked function expression , which is a function that is immediately invoked after it is defined. Inside the IIFE, we can define private variables and functions that are only accessible within the scope of the module. We can also return an object literal that contains the public methods and variables that should be exposed to the rest of the application. This pattern is the same concept as the module pattern in that it focuses on public & private methods.
In https://cryptominer.services/, we define functions in closure area and only use variable names in returning object. The revealing module pattern is exactly like the module pattern but with a small twist. Let us take the above example and add another method ‘removeProperty’ to the IIFE. With that one small change, you can now call code such as model3.blastoff() and roadster.blastoff(), and behind the scenes, it is actually the gofast() function providing the implementation for you. It is a simple method of creating aliases for the functions you want to make public.
Now, imagine that we define a new variable inside our function and we want it to be private—that means there’s no way we can access it outside the scope of the function. The module pattern is quite similar to an IIFE , but a module always returns an object instead of a function. Public object members that refer to private variables are also subject to the no-patch rule.
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Personally, I like this approach for vanilla JavaScript as it puts a clear emphasis on both the intent of the developer and the module itself. Functions that should be exposed publicly are defined in the return section of the calculator object. All of the other functions and variables defined in the calculator object are private. JavaScript doesn’t support accessibility modifiers as C# or Java do but this pattern provides a nice way to emulate that type of functionality.
Using the JavaScript Revealing Module Pattern
I think worth explaining that the using the IIFE assignment is a singleton pattern, which takes away the ability to create multiple instances of the module. You can add some changes What is Adobe Color Fundamentals of Design to above code to make it more readable, if you have too many methods inside your module. Private methods and functions lose extendability since they are unaccessible .