Exports, Imports and module.exports

Exports and module.exports  

“Export” means the outflow of a commodity from one place to another, like exporting goods. So, you know its essential meaning. 

In JavaScript also, it actually implies something similar. Using export, you can use the functions, classes, or any primitive data type as well of the file in another. 
One significant fact to be noted here is that exports and module.exports are in CommonJS module specification. To use these exported modules, we use ‘require’. require() is a topic for a separate article. 

Let’s look at the exports and module.exports.

Usage 

If you remember, in file1.js, we had:

console.log(“Hi! This is file1.js)”);
function user_name(name)
{
	console.log(name +”! You are a Ninja”); 
} 
function user_gender(gender)
{
	console.log(“You are a ”+gender);
}

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Now, export them so that other modules like file2.js can use them(using import, which you have already learned in this article). 

Exporting can be done like this:

module.exports=name of function/class/anything that you want to export

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This contains what we want to export out of the module. A module is an object. By default, the module is encapsulated, so you need to specify whatever we want to take out of it to use in another module. Here, we specify it by using exports.

Let’s say we want to export the user_name() function. So, that will be done in the following way: 

module.exports=user_name; 

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After adding this, file.js will look like this:

console.log(“Hi! This is file1.js)”);
function user_name(name)
{
	console.log(name +”! You are a Ninja”); 
} 
function user_gender(gender)
{
	console.log(“You are a ”+gender);
}
module.exports=user_name; 

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So, it gives the instructions that although the module is encapsulated, it will return user_name(), whenever required. 

But, here the catch is that whenever this module file1.js is required, only the user_name() function will be exported, not the other one. 

To export the other function as well, the following syntax can be followed: 

module.exports={
	user_name: user_name,
	user_gender: user_gender
}; 

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It uses key-value property here. Shorthand notation for the same also exists, which is as follows: 

module.exports={
	user_name,
	user_gender
};  

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Although, there is an alternative to this as well, that is;

exports.user_name=user_name;
exports.user_gender=user_gender; 

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Module.exports has been replaced with exports. This is usually done when we are exporting more than one function, object, etc. from a module. It is equivalent to:

var exports=module.exports; 

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We don’t do it explicitly, JavaScript implicitly implements it. It is kind of reference to module.exports.

But while using ‘exports’ instead of ‘module .exports’, you need to be careful. Let’s say you are just exporting user_name() function and not user_gender() function. So, you write it like this; 

exports=user_name; 

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But, this will give the following error in the module where you require it: 

TypeError: user_name is not a function

Let’s figure out why is this so. 

Recall that ‘exports; is a kind of alias that JavaScript provides you for ‘module.exports’ for your convenience like this: 

var exports=module.exports 

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But when you write exports=user_name, you are no longer updating the exports property of the module object. You are simply trying to replace the alias, which was ‘exports’ to ‘user_name’. No new property was added to module.export. 
Let’s move to a new way of writing it. 

Look at the following code: 

exports.user_name=(name)=>console.log(name +”! You are a Ninja”); 

This is the arrow notation of the function and this also works completely fine. You have added the property ‘user_name’ to exports or say module.exports. You can also practice by yourself with the help of an online JS editor.

Properties

1. Exports and module.exports come under CommonJs specification.

2. Require should be used in this specification for importing

3. Each is considered to have its own scope. The functions and classes in the file are private and invisible to the outside files.

Frequently Asked Questions  

1. What are modules in JavaScript? 
   Modules in JavaScript are files that contain reusable code. This re-usable code can be accessed using export and import statements.
    
2. Is exports=function_name same as module.exports=function_name?
   No, they both are very different things. exports=function_name does not perform any sort of exporting.
    
3. Why is ‘as’ used in import statement?
   It is used to provide meaningful alias to the imported function or objects. 

Conclusion

This article extensively discusses the import, exports and module.exports in JavaScript. We also explain the usage and properties of these in detail. 

We hope that this blog has helped you enhance your knowledge regarding exports, imports and module.exports, and if you would like to learn more, check out our articles on JavaScript. Do upvote our blog to help other ninjas grow. 

Happy Coding!