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.

This feature is only implemented natively in Safari and Chrome at this time. It is implemented in many transpilers, such as the Traceur Compiler, Babel or Rollup.

Syntax

export { name1, name2, …, nameN };
export { variable1 as name1, variable2 as name2, …, nameN };
export let name1, name2, …, nameN; // also var, function
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:
    // exports a function declared earlier
    export { myFunction }; 
    
    // exports a constant
    export const foo = Math.sqrt(2);
  • Default exports (function):
    export default function() {} 
  • Default exports (class):
    export default class {} 

Named exports are useful to export several values. During the import, it is mandatory to use the same name of the corresponding object.

But a default export can be imported with any name for example:

export default k = 12; // in file test.js

import m from './test' // note that we got the freedom to use import m instead of import k, because k was default export

console.log(m);        // will log 12

There can be only one default export

The following syntax does not export a default export from the imported module:

export * from …;

If you need to export the default, write the following instead:

import mod from "mod";
export default mod;

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

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Exports' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Exports' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic Support61151542 No4710.1
FeatureAndroidChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic Support No61 (Yes)542 No4710.1

1. From version 15: this feature is behind the Experimental JavaScript Features preference.

2. From version 54: this feature is behind the dom.moduleScripts.enabled preference. To change preferences in Firefox, visit about:config.

See also