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How to Export a Default Function in JavaScript

Learn how to export a default function in JavaScript and utilize it in other modules.

Last updated on October 5, 2023 at 10:29 AM

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Krste Rajchevski

Software Engineer @ Bugpilot

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JavaScript is a versatile programming language that allows developers to build complex applications with ease. One important aspect of JavaScript is the ability to export and import functions, variables, and objects between different modules. In this guide, we will focus specifically on how to export a default function in JavaScript. This feature allows developers to conveniently export a single function as the default export, making it easier to import and use in other parts of the codebase.

Exporting a Default Function

To export a default function in JavaScript, we can use the export default syntax. This syntax provides a concise and straightforward way to export a single function as the default export of a module.
Consider the following example:

1// greet.js
2
3export default function greet(name) {
4  console.log(`Hello, ${name}
5!`);
6}
7

In the above code snippet, we define a function called greet and export it as the default export of the greet.js module. The export default statement precedes the function declaration, indicating that the function is the default export.

Importing a Default Function

Once we have exported a default function, we can import and use it in other modules. To import the default function, we use the import statement followed by the default keyword.
Let's assume we want to import the greet function from the greet.js module in another file:

1// main.js
2import greet from "./greet.js";
3
4greet("Alice"); // Output: Hello, Alice!
5

In the example above, we use the import statement to import the default export from the greet.js module. The imported function is assigned to the variable greet, allowing us to call it as a regular function.

Exporting a Default Function Along with Other Named Exports

It is worth mentioning that a module can export both a default function and other named exports. This allows us to have a mix of default and named exports within the same module.
Consider the following example:

1// utils.js
2
3export default 
4function utilityFunction() {
5  // Default 
6function
7}
8
9
10export 
11function helperFunction() {
12  // Named 
13function
14}
15

In the utils.js module, we export the utilityFunction as the default export and the helperFunction as a named export. Both of these functions can be imported separately in other modules.

Conclusion

Exporting a default function in JavaScript provides a convenient way to export a single function as the default export of a module. This allows other parts of the codebase to easily import and use the function. We learned how to export a default function using the export default syntax and import it using the import statement. Additionally, we explored how a module can export both a default function and other named exports. By understanding these concepts, developers can effectively utilize default function exports in their JavaScript projects, improving code maintainability and reusability.

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