import

The static import statement is used to import features into JavaScript modules that have been exported by another module. Imported modules are implicitly in strict mode whether you declare them as such or not.

There is also a function-like dynamic import(), which allows modules to be imported dynamically when needed, rather than at the start of the module.

Dynamic imports are useful in situations where you wish to load a module conditionally, or on demand. The static form is preferable for loading initial dependencies, and can benefit more readily from static analysis tools and tree shaking.

Syntax

// Import individual features
import { export } from "module-name";
import { export1 , export2 } from "module-name";

// Import default export
import defaultExport from "module-name";

// Import all of a module's exports as a module object
import * as name from "module-name";

// Import renamed exports 
import { export as alias } from "module-name";

// Import a module for side effects only
import "module-name";

// Combinations
import { export1 , export2 as alias2 , [...] } from "module-name";
import defaultExport, { export [ , [...] ] } from "module-name";
import defaultExport, * as name from "module-name";

// Dynamic module import
var promise = import("module-name"); // This is a stage 3 proposal.

defaultExport

Name that will refer to the default export from the module.

module-name

Path to the module to import from. This is often a relative or absolute path name to the .js file containing the module. Certain bundlers may allow you to omit the .js extension, but native JS modules require it.

name

When a module's exports are imported as a module, this is the name of the module object, which will act as a namespace when referring to the imports.

export, exportN

Name of the exports to be imported.

alias, aliasN

Alternative names that will be used when exports are renamed.

Description

Import a single export from a module

Given an object or value named myExport which has been exported from the module my-module either implicitly (because the entire module is exported) or explicitly (using the export statement), this inserts myExport into the current scope.

import {myExport} from '/modules/my-module.js';

Import multiple exports from module

This inserts both foo and bar into the current scope.

import {foo, bar} from '/modules/my-module.js';

Import an entire module's contents

This inserts myModule into the current scope, containing all the exports from the module in the file located in /modules/my-module.js.

import * as myModule from '/modules/my-module.js';

Here, accessing the exports means using the module name ("myModule" in this case) as a namespace. For example, if the module imported above includes an export doAllTheAmazingThings(), you would call it like this:

myModule.doAllTheAmazingThings();

Rename an export with a more convenient alias

You can rename an export when importing it. For example, this inserts shortName into the current scope.

import {reallyReallyLongModuleExportName as shortName}
  from '/modules/my-module.js';

Rename multiple exports during import

Import multiple exports from a module with convenient aliases.

import {
  reallyReallyLongModuleExportName as shortName,
  anotherLongModuleName as short
} from '/modules/my-module.js';

Import a module for its side effects only

Import an entire module for side effects only, without importing anything. This runs the module's global code, but doesn't actually import any values.

import '/modules/my-module.js';

Importing defaults

It is possible to have a default export (whether it is an object, a function, a class, etc.). The import statement may then be used to import such defaults.

The simplest version directly imports the default:

import myDefault from '/modules/my-module.js';

It is also possible to use the default syntax with the ones seen above (namespace imports or named imports). In such cases, the default import will have to be declared first. For instance:

import myDefault, * as myModule from '/modules/my-module.js';
// myModule used as a namespace

or

import myDefault, {foo, bar} from '/modules/my-module.js';
// specific, named imports

Dynamic imports

The import keyword may be called as a function to dynamically import a module. When used this way, it returns a promise.

import('/modules/my-module.js')
  .then((module) => {
    // Do something with the module.
  });

This form also supports the await keyword.

let module = await import('/modules/my-module.js');

Applying modules to HTML

To apply a module script to an HTML document, you need to use a <script> of type="module". The import statement cannot be used in non-module scripts. for example:

<script type="module" src="main.js"></script>

Backwards compatibility

Backward compatibility can be put in place by using your type="module" <script> element along with a fallback <script> element containing the nomodule attribute.

<script type="module" src="main.js"></script>
<script nomodule src="fallback.js"></script>

This works because browsers that support JavaScript modules ignore scripts with nomodule set on them, whereas non-supporting browsers will not load the module script and load the fallback instead.

Examples

Standard Import

The code below shows how to import from a secondary module to assist in processing an AJAX JSON request.

The module: file.js

function getJSON(url, callback) {
  let xhr = new XMLHttpRequest();
  xhr.onload = function () { 
    callback(this.responseText) 
  };
  xhr.open('GET', url, true);
  xhr.send();
}

export function getUsefulContents(url, callback) {
  getJSON(url, data => callback(JSON.parse(data)));
}

The main program: main.js

import { getUsefulContents } from '/modules/file.js';

getUsefulContents('http://www.example.com',
    data => { doSomethingUseful(data); });

Dynamic Import

This example shows how to load functionality on to a page based on a user action, in this case a button click, and then call a function within that module. This is not the only way to implement this functionality. The import() function also supports await.

const main = document.querySelector("main");
for (const link of document.querySelectorAll("nav > a")) {
  link.addEventListener("click", e => {
    e.preventDefault();

    import('/modules/my-module.js')
      .then(module => {
        module.loadPageInto(main);
      })
      .catch(err => {
        main.textContent = err.message;
      });
  });
}

Specifications

Browser compatibility

See also

• export
• import.meta
• JavaScript modules guide
• ES6 in Depth: Modules, Hacks blog post by Jason Orendorff
• ES modules: A cartoon deep-dive, Hacks blog post by Lin Clark
• Axel Rauschmayer's book: "Exploring JS: Modules"