Some Random Notes

export default

2 min read

0.

Step 1: Export the component 

The export default prefix is a standard JavaScript syntax (not specific to React). It lets you mark the main function in a file so that you can later import it from other files. (More on importing in Importing and Exporting Components!)

1.

In React, the bundler or testing environment needs the export default keyword so that other files (or the challenge runner itself) can import and render the component. If you remove export default and just write function Profile(), the runner wouldn’t know which component to display as the root, which is why the challenge description notes that the sandbox fails without it.

2. what does export default do ?

export default is a JavaScript (ES6) mechanism used to share functions, objects, or primitive values from one file (module) so that other files can load and use them via import.

In React, it plays a specific role in how components are structured and rendered:

1. Marking the Main Thing to Import

When you write export default function Profile(), you are designating Profile as the primary export of that file.

  • Because it’s the default export, the file importing it doesn’t need to know its exact original name.
  • When another file imports it, it can name it whatever it wants (e.g., import MyComponent from './Profile.js').

2. Enabling the Sandbox/App Runner to Find It

React applications are built out of trees of components. When a tool, bundler, or React framework runs your code, it needs an entry point—a root component to render onto the screen (like App or Profile).

  • If a component function is defined as a regular function (function Profile()) without being exported, it is trapped inside that single file and remains entirely invisible to the rest of the application.
  • Adding export default tells the module system: “Take this component and make it available globally to whoever imports this file.”

Comparison: Default vs. Named Exports

  • Default Export (export default): You can only have one default export per file. When importing, you don’t use curly braces:
import Profile from './Profile.js';
  • Named Export (export): You can have multiple named exports per file. When importing, you must use exact curly braces matching the export name:
// In Button.js
export function PrimaryButton() { ... }
export function SecondaryButton() { ... }
 
// In App.js
import { PrimaryButton, SecondaryButton } from './Button.js';

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