I want to ask what the last sentence means and does (export default HelloWorld;) but I can't find any tutorials about it.
// hello-world.jsx
import React from 'react';
class HelloWorld extends React.Component {
render() {
return <p>Hello, world!</p>;
}
}
export default HelloWorld;
This question is related to
javascript
reactjs
Simplest Understanding for default export
is
Export
is ES6's feature which is used to Export a module(file) and use it in some other module(file).
Default Export:
default export
is the convention if you want to export only one object(variable, function, class) from the file(module).Export or Named Export:
It is used to export the object(variable, function, calss) with the same name.
It is used to export multiple objects from one file.
It cannot be renamed when importing in another file, it must have the same name that was used to export it, but we can create its alias by using as
operator.
In React, Vue and many other frameworks the Export is mostly used to export reusable components to make modular based applications.
In simple word export means letting the script we wrote to be used by another script. If we say export, we mean any module can use this script by importing it.
In Simple Words -
The export statement is used when creating JavaScript modules to export functions, objects, or primitive values from the module so they can be used by other programs with the import statement.
Here is a link to get clear understanding : MDN Web Docs
export default
is used to export a single class, function or primitive from a script file.
The export can also be written as
export default class HelloWorld extends React.Component {
render() {
return <p>Hello, world!</p>;
}
}
You could also write this as a function component like
export default const HelloWorld = () => (<p>Hello, world!</p>);
This is used to import this function in another script file
import HelloWorld from './HelloWorld';
You don't necessarily import it as HelloWorld
you can give it any name as it's a default export
As the name says, it's used to export functions, objects, classes or expressions from script files or modules
Utiliites.js
export function cube(x) {
return x * x * x;
}
export const foo = Math.PI + Math.SQRT2;
This can be imported and used as
App.js
import { cube, foo } from 'Utilities';
console.log(cube(3)); // 27
console.log(foo); // 4.555806215962888
Or
import * as utilities from 'Utilities';
console.log(utilities.cube(3)); // 27
console.log(utilities.foo); // 4.555806215962888
When export default is used, this is much simpler. Script files just exports one thing. cube.js
export default function cube(x) {
return x * x * x;
};
and used as App.js
import Cube from 'cube';
console.log(Cube(3)); // 27
Let's see the code of how we can use this
import react from 'react'
function Header()
{
return <p><b><h1>This is the Heading section</h1></b></p>;
}
**export default Header;**
Source: Stackoverflow.com