export

The export statement is used to export functions, objects or primitives from a given file (or module).

Syntax

export { name1, name2, …, nameN };
export { variable1 as name1, variable2 as name2, …, nameN };
export let name1, name2, …, nameN; // also var
export let name1 = …, name2 = …, …, nameN; // also var, const

export default expression;
export default function (…) { … } // also class, function*
export default function name1(…) { … } // also class, function*
export { name1 as default, … };

export * from …;
export { name1, name2, …, nameN } from …;
export { import1 as name1, import2 as name2, …, nameN } from …;

nameN

Identifier to be exported (so that it can be imported via import in another script).

Description

There are two different types of export, each type corresponds to one of the above syntax:

• Named exports:

  export { myFunction }; // exports a function declared earlier
  export const foo = Math.sqrt(2); // exports a constant

• Default exports (only one per script):

  export default function() {} // or 'export default class {}'
  // there is no semi-colon here

Named exports are useful to export several values. During the import, one will be able to use the same name to refer to the corresponding value.

Concerning the default export, there is only a single default export per module. A default export can be a function, a class, an object or anything else. This value is to be considered as the "main" exported value since it will be the simplest to import.

Examples

Using named exports

In the module, we could use the following code:

// module "my-module.js"
function cube(x) {
  return x * x * x;
}
const foo = Math.PI + Math.SQRT2;
export { cube, foo };

This way, in another script (cf. import), we could have:

import { cube, foo } from 'my-module';
console.log(cube(3)); // 27
console.log(foo);    // 4.555806215962888

Using the default export

If we want to export a single value or to have a fallback value for our module, we could use a default export:

// module "my-module.js"
export default function cube(x) {
  return x * x * x;
}

Then, in another script, it will be straightforward to import the default export:

import cube from 'my-module';
console.log(cube(3)); // 27

Note that it is not possible to use var, let or const with export default.

Specifications

Browser compatibility

See also

• import
• ES6 in Depth: Modules, Hacks blog post by Jason Orendorff
• Axel Rauschmayer's book: "Exploring JS: Modules"