80

introduction

If you’ve used JavaScript, you’ve probably come across this term. export default And I wondered what it was and how it worked. This Byte of his is aimed at developers who want to understand the basics of JavaScript and deepen their knowledge of the language’s intricacies. Let’s take a closer look at JavaScript modules and their concepts. export default. Eventually, you’ll have a better understanding of when and how to use it. export default to your code.

Understand JavaScript modules

JavaScript modules are self-contained code that can be exported and imported into other JavaScript files. They help keep your code organized, maintainable, and reusable. JavaScript modules were introduced in his ES6 and have been at the core of modern JavaScript development ever since.

Consider the following example.

// mathFunctions.js
const add = (a, b) => a + b;
const subtract = (a, b) => a - b;

export  add, subtract ;

In the above code there is a module named. mathFunctions.js This exports two functions. add and subtract.

// app.js
import  add, subtract  from './mathFunctions.js';

console.log(add(2, 3));  // Output: 5
console.log(subtract(5, 2));  // Output: 3

in app.jsimport. add and subtract function from mathFunctions.js Please use as necessary.

What are “export defaults”?

export default Syntax used in JavaScript modules to export a single entity (function, object, variable). Default Export from module.

Consider the following example.

// greeting.js
const greeting = 'Hello, StackAbuse readers!';

export default greeting;

In the above code there is a module named. greeting.js export a single string greeting as the default export.

// app.js
import greeting from './greeting.js';

console.log(greeting);  // Output: Hello, StackAbuse readers!

in app.jsImport the default export from . greeting.js Please use as necessary. Notice that I don’t use curly braces Import the default export. this is the purpose default keyword.

This is similar to the method you use exports.greeting = ... versus module.exports = ... At the node.

When and how to use Default Export

export default Typically used when a module has only one thing to export. This can be a function, class, object, or anything else that is the main focus of the module.

Consider the case where we have a module that exports a single function.

// sayHello.js
const sayHello = name => `Hello, $name!`;

export default sayHello;

And import it into another module.

// app.js
import sayHello from './sayHello.js';

console.log(sayHello('StackAbuse readers'));  // Output: Hello, StackAbuse readers!

In this case, it makes sense to use the “default export”. sayHello teeth, sayHello.js Modules are exported, so you don’t need to use structured assignment to access functions.

Remember whether to use export default or named exports, it really depends on how you want to structure your code. Both have their uses, and understanding when to use each is key to mastering JavaScript modules.

Common errors regarding “default export”

So what are some common pitfalls and errors you might come across? Here’s a little bit about possible mistakes. Depending on your JS experience level, you may encounter one or more of the following issues:

One common mistake is to export default Multiple times within the same module. Remember, export default Refers to a single value, such as a function, object, or variable.

// Incorrect usage!
export default let name = "John";
export default let age = 25;

Another common mistake is the use of curly braces. Use “Default Export”. This is unnecessary and will result in a syntax error.

// Incorrect usage!
import  myFunction  from './myModule.js';

Fixing “default export” error

Now that we’ve looked at some common pitfalls, let’s talk about how to fix them.

If you are trying to export multiple values ​​from a module using export defaultconsider combining them to create objects.

// Correct usage
let name = "John";
let age = 25;
export default  name, age ;

Regarding the second error, remember the following: export default No curly braces are needed. The correct way to import the default export is:

// Correct usage
import myFunction from './myModule.js';

named export

meanwhile export default is a useful tool, but it is not the only way to export values ​​from a JavaScript module. Named exports are a good alternative, especially when exporting multiple values.

In contrast to default exports, named exports allow you to export multiple values. Each of these exports is syntax.

// Named exports
export const name = "John";
export const age = 25;

And you can import it like this:

// Importing named exports
import  name, age  from './myModule.js';

conclusion

In this byte, export default You reviewed JavaScript statements, investigated some common errors, and learned how to fix them. We also discussed named exports, a similar but different concept. The more you understand, the fewer export/import problems you will have in your JS code.