Creating and Exporting Modules in Node.js

Create Module

As we are familiar with the reason behind the modules' existence, let us learn how we can create a module inside node JS.

To do so, we just have to create a new file, module.js, and then write the same function there. Let's have a look.

module.js

• JS

JS

function concatenation(x, y) {
  return x + y;
}

You can also try this code with Online Javascript Compiler

Run Code

index.js

• JS

JS

var myWord = concatenation("Coding ", "Ninjas");
console.log(myWord);

You can also try this code with Online Javascript Compiler

Run Code

Output:

Explanation:

Error! "concatenation is not defined". Just by doing the cut-paste task, we can face an error like this. We are facing this error because we have not yet linked our module.js file to the index.js file.

Import Module

A module can be imported, and its functionality can be reused. Node.js has the built-in require() function, which is the simplest way to use modules from the existing separate files. The basic functionality of require() is that it reads a JavaScript file, executes it, and proceeds to return the export object.

Hence, we will use a require() function to resolve the above error. Let's try again the same example with the require() function.

module.js

• JS

JS

function concatenation(x, y) {
  return x + y;
}

You can also try this code with Online Javascript Compiler

Run Code

index.js

• JS

JS

var myModule = require("./module");

var myWord = myModule.concatenation("Coding ", "Ninjas");
console.log(myWord);

You can also try this code with Online Javascript Compiler

Run Code

Output:

Explanation:

Oops! Again an error? But the error is different here. The error says, "myModule.concatenation is not a function". The program is showing an error because we have to call the export() function to use any function outside the file.

Export Module

The module.exports is a special object of a Javascript file in Node.js by default. Here the module is a variable that defines the current modules. And the exports() function is an object that will be exported as a module. So whatever we assign to the module.exports, it will be exported as a module. 

We can resolve the error that came in the last section by using the exports() function. Let's have a look.

module.js

• JS

JS

function concatenation(x, y) {
  return x + y;
}


module.exports.concatenation = concatenation;

You can also try this code with Online Javascript Compiler

Run Code

index.js

• JS

JS

var myModule = require("./module");

var myWord = myModule.concatenation("Coding ", "Ninjas");
console.log(myWord);

You can also try this code with Online Javascript Compiler

Run Code

Output:

Explanation:

We have used the module.exports function inside the module.js file to export the function to the main index.js file. 

Now the question is, "Can we export multiple functions at a time?" The answer is Yes. Let's check them out.

Note: There are two ways to export multiple functions in Node JS. 

Single Format

One way to export multiple functions is to write the "module.exports" for each function line by line. Let's take an example of this.

module.js

• JS

JS

function concatenation(x, y) {
  return x + y;
}

function greet(x) {
  return x;
}

module.exports.concatenation = concatenation;
module.exports.greet = greet;

You can also try this code with Online Javascript Compiler

Run Code

index.js

• JS

JS

var myModule = require("./module");

var myWord = myModule.concatenation("Coding ", "Ninjas");
console.log(myWord);

var myGreet = myModule.greet("Welcome to Coding Ninajs");
console.log(myGreet);

You can also try this code with Online Javascript Compiler

Run Code

Output:

Explanation:

As you can see, both functions are exported separately in the module.js file. But writing the same lines for each function in a huge project will be a tough task. 

To overcome this problem, we have the array format also. Let's have a look.

Array Format

In the array format, we can export multiple functions at a time just by writing the function name. Let's quickly move to the example for better understanding.

module.js

• JS

JS

function concatenation(x, y) {
  return x + y;
}

function greet(x) {
  return x;
}

module.exports = { concatenation, greet };

You can also try this code with Online Javascript Compiler

Run Code

index.js

• JS

JS

var myModule = require("./module");

var myWord = myModule.concatenation("Coding ", "Ninjas");
console.log(myWord);

var myGreet = myModule.greet("Welcome to Coding Ninajs");
console.log(myGreet);

You can also try this code with Online Javascript Compiler

Run Code

Output:

Explanation:

The output will remain the same for the array format also. Additionally, this will save time too for the user. Hence, this is a good practice to use the array format instead of a single format.

As we have now discussed all our topics, let's now discuss some faqs.

Frequently Asked Questions

What is module export in Node.js?

Module export in Node.js allows sharing functions, objects, or variables from one file to another using module.exports or exports.

What is the difference between module.exports and exports?

module.exports is the actual object exported from a module, while exports is a shorthand reference that points to module.exports by default.

How to export a module function in JavaScript?

Export a function in JavaScript using module.exports = functionName; or exports.functionName = functionName; in Node.js, or export in ES6 modules.

Conclusion

This article discusses the topic of how to create and export modules in node js. In detail, we have seen the definition module. Along with this, we have seen how to create, import and export the modules with examples.

We hope this blog has helped you enhance your knowledge to create and export modules in node js. If you want to learn more, then check out our articles.

• Introduction to Node.js
• Features of Node.js
• Django vs Node.js

And many more on our platform Code360.

Refer to our Guided Path to upskill yourself in DSA, Competitive Programming, JavaScript, System Design, and many more! If you want to test your coding ability, you may check out the mock test series and participate in the contests hosted on Code360!

But suppose you have just started your learning process and are looking for questions from tech giants like Amazon, Microsoft, Uber, etc. In that case, you must look at the problems, interview experiences, and interview bundles for placement preparations.

However, you may consider our paid courses to give your career an edge over others!