How to use the require() Function in JavaScript?

In this article, we will understand the require() function in JavaScript.

The require() function is a built-in function in JavaScript. It is an essential part of CommonJS module system which is used to import modules and lets you utilize external modules in your code.

Modules are similar to JavaScript library but modules are small consisting of a piece of code. It contains classes and function which aids in improving the code and helps in keeping the code in an organized manner. These modules can be built-in or customized. We can import both built-in and customized modules and use it when required. We sometimes need to import external module from the web and we can do that by utilizing the web-based location.

How to use the require() function?

It is simple to use the require() function. We have to simply assign a function to a variable.

General syntax:

In the above syntax, var_name is the name of the variable, require() is the function containing location name as the argument.

Syntax for importing external modules:

In the above syntax, my_var is the name of the variable, require() is the function containing external location as the argument.

Syntax for importing a local file:

In the above syntax, my_var is the name of the variable, require() is the function containing the location of local file as the argument which is denoted by dot notation which defines the root location of the folder.

CommonJS and ESM Module formats

The CommonJS module was the default module in the Node.js ecosystem for a long time but a new module called ECMAScript module is also utilized. Both of these modules work with Node.js without any problem but their execution is different from each other.

CommonJS

It is the default module format in Node.js which imports modules with the help of the require() function and the module.exports object.

Example

Let us understand it with the help of examples.

//file1.js

We have made a file named file1.js which consists of function add. The module.exports is an object in Node.js which defines what tools we want to allow.

//file2.js

We have used a require('./file') function which imports add function from the file1.js. Now, we do not need to write the whole code again. We have simply imported the function and used it when required.

Output:

 
63

ECMAScript Modules (ESM)

The ECMAScript module was introduced in ECMAScript 2015 and it is a modern module format. It is now supported in modern browsers. It utilizes keywords such as import and export which is used to import modules.

Example:

//greetings.mjs

//index.mjs

Output:

 
Hi, Javatpoint!

Note: Old browsers may not support ECMAScript module so you may require to utilized bundler such as Browserify and Webpack or any other alternative.

Conclusion:

We have understood the require() function in JavaScript in this article. This function is an amazing tool for organizing and maintaining code properly.