JavaScript Modules- Concept and Scope
In case you haven't had any idea, a JavaScript module enables developers to divide their codebases into smaller or lets say modular encapsulated components. Each module may include variables, functions, classes that correlate respectively in terms of completing a task or serving a specific feature. This separation makes it possible to create, run tests, and maintain high-level, advanced applications. Earlier, developers had to struggle since JavaScript did not support modules. So all the functions and variables were globally stored which became a hassle to manage which eventually had a lot of errors.To solve these problems, the module system was one of the features added to JavaScript. Now, thanks to modules, developers can bundle the code in different files and import and export sections of code where they are necessary. This modular development enhances code but also prevents complications that arise from variables being global.
What are JavaScript Modules and How Do They Work?
JavaScript modules export and import code from one another. This is one of the solutions that these modules provide.1. Exporting
There are two types of exports: named exports and default exports.First, code from one of the modules must be exported in order for it to be used by other modules.
- Named Exports : These are helpful in exporting more than one object or a function from the module. In order to export, the `export` keyword is written before the particular function or the variable that you want to export.
Named Exports Example
// math.js
export const add = (a, b) => a + b;
export const subtract = (a, b) => a - b; - Default Exports : This enables a module to implement sole default export whether it's a function class, or an object the module is restricted to a single default export.
Default Exports Example
//Dummy.js
const logger = (message) => {
console.log(message);
}
export default logger; 2. Importing
When a code is exported from an inter module, it can then be imported using the `import` syntax to other intermodules within the project connected via the statement.- Importing Named Exports : While recalling a named export, the bracket curly must be in the same syntax as the named export.
Importing Named Exports Example
//Dummy2.js
import {add, subtract} from './math.js';
console.log(add(2,3)); //5
console.log(subtract(5,3)); //2 - Importing Default Exports : Importing the said module does not require the use of the export mention since there is and can only be one default export which is common in every module.
Importing Default Exports Example
//app.js
import logMessage from './logger.js';
logMessage('This is a log message!'); Benefits of Using JavaScript Modules
There are quite a number of benefits of using modules in JavaScript as listed below:1. Better Code Structure
It might be a bit hard to handle all the codes that are written in one file as projects get larger and more complex. That's why the use of modules is important, because they allow you to separate codes logically and by their purpose and this makes the logical structure much easier to comprehend. For instance, all logic regarding user authentication could reside within a module and all logic concerning interactions with the database could reside within another module. In that case, developers could develop only one aspect of the application at a time.2. Avoiding Code Duplication
After creating each utility function, it gets easy to reuse or call it in any part of your application. For example, suppose a module is created that formats dates, and this module is subsequently imported into various others. In this case, all would be well because calling multiple copies of a module adds nothing and increases complexity without adding benefit. This decreases replications and increases manageability since changing the utility function would only have to be done in one spot.3. Minimizing Global Namespace Pollution
The major problem with traditional JavaScript is its use of global variables and functions, as this allows multiple parts of the program to use the same variable or function which causes conflicts and bugs. On the contrary, modules provide a way in which the variables and functions defined by you are defined into the range of the module and this minimizes the risk of conflicts whilst maintaining the neatness of the easier Javascript namespace.4. Simplified Testing And Debugging
As a result of modules containing or encapsulating a certain set of features, it becomes easy to test and identify problems in pieces of code without interfering with other parts of the application. For instance, with the help of an in-built debugger such as Chrome DevTools, if a bug develops in a single feature of a program, the only part that will be affected is the module that facilitates that feature, and thus the debugging is done in a targeted manner without affecting the whole program.5. The Use Of Dynamic Imports
The good thing about JavaScript modules is that you can use the dynamic type of imports alongside it, which allows you to import modules dynamic imports equates to the ability to only pull modules when they are actually needed; this comes in handy when you want to reduce the application's initial loading duration when needed. Frameworks that allow for lazy loading/large applications will particularly benefit from the use of dynamic imports.Dynamic Imports Example
button.addEventListener('click', () => {
import('./notThatSmallModule.js').then(module => {
module.testButton();
});
}); This pattern of code will allow you to break down your code into various small blocks that will load whenever they are needed instead of loading all at once.
ES6 Modules and the ` ` tag. By doing this, you assist the browser in decoding the script as a module allowing for the `import` and `export` elements to be used.
Using Modules in HTML
This tells the browser that `app.js` is a module and that it should be handled and implemented in that manner as well. This also makes sure that the module is always loaded with its own scope so that there is no risk of overwriting the global namespace.
Using Modules in HTML
