How to Include Js File in Another Js File

How do I include a JavaScript file in another JavaScript file?

The old versions of JavaScript had no import, include, or require, so many different approaches to this problem have been developed.

But since 2015 (ES6), JavaScript has had the ES6 modules standard to import modules in Node.js, which is also supported by most modern browsers.

For compatibility with older browsers, build tools like Webpack and Rollup and/or transpilation tools like Babel can be used.

ES6 Modules

ECMAScript (ES6) modules have been supported in Node.js since v8.5, with the --experimental-modules flag, and since at least Node.js v13.8.0 without the flag. To enable "ESM" (vs. Node.js's previous CommonJS-style module system ["CJS"]) you either use "type": "module" in package.json or give the files the extension .mjs. (Similarly, modules written with Node.js's previous CJS module can be named .cjs if your default is ESM.)

Using package.json:

{
    "type": "module"
}

Then module.js:

export function hello() {
  return "Hello";
}

Then main.js:

import { hello } from './module.js';
let val = hello();  // val is "Hello";

Using .mjs, you'd have module.mjs:

export function hello() {
  return "Hello";
}

Then main.mjs:

import { hello } from './module.mjs';
let val = hello();  // val is "Hello";

ECMAScript modules in browsers

Browsers have had support for loading ECMAScript modules directly (no tools like Webpack required) since Safari 10.1, Chrome 61, Firefox 60, and Edge 16. Check the current support at caniuse. There is no need to use Node.js' .mjs extension; browsers completely ignore file extensions on modules/scripts.

<script type="module">
  import { hello } from './hello.mjs'; // Or the extension could be just `.js`
  hello('world');
</script>

// hello.mjs -- or the extension could be just `.js`
export function hello(text) {
  const div = document.createElement('div');
  div.textContent = `Hello ${text}`;
  document.body.appendChild(div);
}

Read more at https://jakearchibald.com/2017/es-modules-in-browsers/

Dynamic imports in browsers

Dynamic imports let the script load other scripts as needed:

<script type="module">
  import('hello.mjs').then(module => {
      module.hello('world');
    });
</script>

Read more at https://developers.google.com/web/updates/2017/11/dynamic-import

Node.js require

The older CJS module style, still widely used in Node.js, is the module.exports/require system.

// mymodule.js
module.exports = {
   hello: function() {
      return "Hello";
   }
}

// server.js
const myModule = require('./mymodule');
let val = myModule.hello(); // val is "Hello"

There are other ways for JavaScript to include external JavaScript contents in browsers that do not require preprocessing.

AJAX Loading

You could load an additional script with an AJAX call and then use eval to run it. This is the most straightforward way, but it is limited to your domain because of the JavaScript sandbox security model. Using eval also opens the door to bugs, hacks and security issues.

Fetch Loading

Like Dynamic Imports you can load one or many scripts with a fetch call using promises to control order of execution for script dependencies using the Fetch Inject library:

fetchInject([
  'https://cdn.jsdelivr.net/momentjs/2.17.1/moment.min.js'
]).then(() => {
  console.log(`Finish in less than ${moment().endOf('year').fromNow(true)}`)
})

jQuery Loading

The jQuery library provides loading functionality in one line:

$.getScript("my_lovely_script.js", function() {
   alert("Script loaded but not necessarily executed.");
});

Dynamic Script Loading

You could add a script tag with the script URL into the HTML. To avoid the overhead of jQuery, this is an ideal solution.

The script can even reside on a different server. Furthermore, the browser evaluates the code. The <script> tag can be injected into either the web page <head>, or inserted just before the closing </body> tag.

Here is an example of how this could work:

function dynamicallyLoadScript(url) {
    var script = document.createElement("script");  // create a script DOM node
    script.src = url;  // set its src to the provided URL
   
    document.head.appendChild(script);  // add it to the end of the head section of the page (could change 'head' to 'body' to add it to the end of the body section instead)
}

This function will add a new <script> tag to the end of the head section of the page, where the src attribute is set to the URL which is given to the function as the first parameter.

Both of these solutions are discussed and illustrated in JavaScript Madness: Dynamic Script Loading.

Detecting when the script has been executed

Now, there is a big issue you must know about. Doing that implies that you remotely load the code. Modern web browsers will load the file and keep executing your current script because they load everything asynchronously to improve performance. (This applies to both the jQuery method and the manual dynamic script loading method.)

It means that if you use these tricks directly, you won't be able to use your newly loaded code the next line after you asked it to be loaded, because it will be still loading.

For example: my_lovely_script.js contains MySuperObject:

var js = document.createElement("script");

js.type = "text/javascript";
js.src = jsFilePath;

document.body.appendChild(js);

var s = new MySuperObject();

Error : MySuperObject is undefined

Then you reload the page hitting F5. And it works! Confusing...

So what to do about it ?

Well, you can use the hack the author suggests in the link I gave you. In summary, for people in a hurry, he uses an event to run a callback function when the script is loaded. So you can put all the code using the remote library in the callback function. For example:

function loadScript(url, callback)
{
    // Adding the script tag to the head as suggested before
    var head = document.head;
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = url;

    // Then bind the event to the callback function.
    // There are several events for cross browser compatibility.
    script.onreadystatechange = callback;
    script.onload = callback;

    // Fire the loading
    head.appendChild(script);
}

Then you write the code you want to use AFTER the script is loaded in a lambda function:

var myPrettyCode = function() {
   // Here, do whatever you want
};

Then you run all that:

loadScript("my_lovely_script.js", myPrettyCode);

Note that the script may execute after the DOM has loaded, or before, depending on the browser and whether you included the line script.async = false;. There's a great article on Javascript loading in general which discusses this.

Source Code Merge/Preprocessing

As mentioned at the top of this answer, many developers use build/transpilation tool(s) like Parcel, Webpack, or Babel in their projects, allowing them to use upcoming JavaScript syntax, provide backward compatibility for older browsers, combine files, minify, perform code splitting etc.

Include a JS file directly in another?

Typically, a build process is used to create a JS bundle that would extract and combine all of the required code from multiple files (see Parcel or ESBuild).

Without a build process, modern JS modules (also known as "ES modules") could be imported using <script type="module">. JQuery can be avoided entirely in 2020 and beyond.

library.js

const name = 'Jane Doe'

export {
  name
}

main.js

import { name } from './library.js'

function sayHello() {
  console.log(`hello ${name}!`)
}

window.addEventListener('DOMContentLoaded', event => {
  document.querySelector('button').addEventListener('click', sayHello)
})

index.html

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

<button>Say Hello</button>

How to include js file in another js file?

You can only include a script file in an HTML page, not in another script file. That said, you can write JavaScript which loads your "included" script into the same page:

var imported = document.createElement('script');
imported.src = '/path/to/imported/script';
document.head.appendChild(imported);

There's a good chance your code depends on your "included" script, however, in which case it may fail because the browser will load the "imported" script asynchronously. Your best bet will be to simply use a third-party library like jQuery or YUI, which solves this problem for you.

// jQuery
$.getScript('/path/to/imported/script.js', function()
{
    // script is now loaded and executed.
    // put your dependent JS here.
});

Include a JS file in another JS file with pure JS

Since you don't want to use modules you could load an additional script with an AJAX call and then use eval to run it. This is the most straightforward way, but it is limited to your domain because of the JavaScript sandbox security model. Using eval also opens the door to bugs, hacks, and security issues.
you can do it like so:

function getFile(filePath) {
    var httpRequest = new XMLHttpRequest();

    if (!httpRequest) {
      alert('Cannot create an XMLHTTP instance');
      return false;
    }

    httpRequest.onreadystatechange = function() {
      if (httpRequest.readyState === XMLHttpRequest.DONE) {
        if (httpRequest.status === 200) {
          eval(httpRequest.responseText);
        } else {
          alert('There was a problem with the request.');
        }
      }
    };

    httpRequest.open('GET', filePath);
    httpRequest.send();
}

getFile('./components/navbar.js');

Import functions from another js file. Javascript

The following works for me in Firefox and Chrome. In Firefox it even works from file:///

models/course.js

export function Course() {
    this.id = '';
    this.name = '';
};

models/student.js

import { Course } from './course.js';

export function Student() {
    this.firstName = '';
    this.lastName = '';
    this.course = new Course();
};

index.html

<div id="myDiv">
</div>
<script type="module">
    import { Student } from './models/student.js';

    window.onload = function () {
        var x = new Student();
        x.course.id = 1;
        document.getElementById('myDiv').innerHTML = x.course.id;
    }
</script>

how to import external js file when using bootstrap?

Remove the include js from the head, <link> tag is used to include css files, <script> tag is used for js files.

After </nav>, where nav ends insert these two lines

<script src="../js/jquery-1.11.0.js"></script>
<script src="../js/index.js"></script>

You are good to go

Importing an external js file into another external js file

add type="module" to your app.ja ( main script)

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

seperate function and export do it like that (more readable):

function ShowAlert(val) { alert(val); } export { ShowAlert }

If you would lieke to export more functions do it liek that:

 export { ShowAlert ,  ShowAlert1 , ShowAlert2 , ShowAlert2}

Run your script on HTTP serwer

Javascript - Issue passing object from one JS file to another JS file

Bro, i've noted two mistakes on your code:

When you import and link your file on your .js and .html files you are pointing to the system root folder (eg. type="/main.js", import { sitesMod } from "/sites.js"; ). To point to the actual folder where are your folder use ./main.js for example and not just /, or just remove it, are the same;
When you declare a variable inside a function it have a local scope and at the final of the execution is deleted, so you can not acess it outside of the scope, so:

import { sitesMod } from "/sites.js";
sitesMod();

console.log(sites);

Are wrong. Instead there are two ways:

At your site.js:

function sitesMod() {
  var sites = [
    'https://site1.org/',
    'https://site2.org/',
    'site3.org/'
  ];

  return sites;
}

At main.js:

import { sitesMod } from "./sites.js";

console.log(sitesMod());

Include a console.log() directly inside the function — the first is better ;):

function sitesMod() {
  var sites = [
    'https://site1.org/',
    'https://site2.org/',
    'site3.org/'
  ];

  console.log(sites);
}

export { sitesMod };

Tip: see more about scope and the difference between var, let and const and also more about Linux (you will understanding the / and ./) and a such more.

I hope it helped you, good studies XD

My english is a sucks, so forgive me for something...

How do I include a JavaScript file in another JavaScript file?

The old versions of JavaScript had no import, include, or require, so many different approaches to this problem have been developed.

But since 2015 (ES6), JavaScript has had the ES6 modules standard to import modules in Node.js, which is also supported by most modern browsers.

For compatibility with older browsers, build tools like Webpack and Rollup and/or transpilation tools like Babel can be used.

ES6 Modules

Using package.json:

{
    "type": "module"
}

Then module.js:

export function hello() {
  return "Hello";
}

Then main.js:

import { hello } from './module.js';
let val = hello();  // val is "Hello";

Using .mjs, you'd have module.mjs:

export function hello() {
  return "Hello";
}

Then main.mjs:

import { hello } from './module.mjs';
let val = hello();  // val is "Hello";

ECMAScript modules in browsers

<script type="module">
  import { hello } from './hello.mjs'; // Or the extension could be just `.js`
  hello('world');
</script>

// hello.mjs -- or the extension could be just `.js`
export function hello(text) {
  const div = document.createElement('div');
  div.textContent = `Hello ${text}`;
  document.body.appendChild(div);
}

Read more at https://jakearchibald.com/2017/es-modules-in-browsers/

Dynamic imports in browsers

Dynamic imports let the script load other scripts as needed:

<script type="module">
  import('hello.mjs').then(module => {
      module.hello('world');
    });
</script>

Read more at https://developers.google.com/web/updates/2017/11/dynamic-import

Node.js require

The older CJS module style, still widely used in Node.js, is the module.exports/require system.

// mymodule.js
module.exports = {
   hello: function() {
      return "Hello";
   }
}

// server.js
const myModule = require('./mymodule');
let val = myModule.hello(); // val is "Hello"

There are other ways for JavaScript to include external JavaScript contents in browsers that do not require preprocessing.

AJAX Loading

Fetch Loading

Like Dynamic Imports you can load one or many scripts with a fetch call using promises to control order of execution for script dependencies using the Fetch Inject library:

fetchInject([
  'https://cdn.jsdelivr.net/momentjs/2.17.1/moment.min.js'
]).then(() => {
  console.log(`Finish in less than ${moment().endOf('year').fromNow(true)}`)
})

jQuery Loading

The jQuery library provides loading functionality in one line:

$.getScript("my_lovely_script.js", function() {
   alert("Script loaded but not necessarily executed.");
});

Dynamic Script Loading

You could add a script tag with the script URL into the HTML. To avoid the overhead of jQuery, this is an ideal solution.

Here is an example of how this could work:

function dynamicallyLoadScript(url) {
    var script = document.createElement("script");  // create a script DOM node
    script.src = url;  // set its src to the provided URL
   
    document.head.appendChild(script);  // add it to the end of the head section of the page (could change 'head' to 'body' to add it to the end of the body section instead)
}

This function will add a new <script> tag to the end of the head section of the page, where the src attribute is set to the URL which is given to the function as the first parameter.

Both of these solutions are discussed and illustrated in JavaScript Madness: Dynamic Script Loading.

Detecting when the script has been executed

It means that if you use these tricks directly, you won't be able to use your newly loaded code the next line after you asked it to be loaded, because it will be still loading.

For example: my_lovely_script.js contains MySuperObject:

var js = document.createElement("script");

js.type = "text/javascript";
js.src = jsFilePath;

document.body.appendChild(js);

var s = new MySuperObject();

Error : MySuperObject is undefined

Then you reload the page hitting F5. And it works! Confusing...

So what to do about it ?

function loadScript(url, callback)
{
    // Adding the script tag to the head as suggested before
    var head = document.head;
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = url;

    // Then bind the event to the callback function.
    // There are several events for cross browser compatibility.
    script.onreadystatechange = callback;
    script.onload = callback;

    // Fire the loading
    head.appendChild(script);
}

Then you write the code you want to use AFTER the script is loaded in a lambda function:

var myPrettyCode = function() {
   // Here, do whatever you want
};

Then you run all that:

loadScript("my_lovely_script.js", myPrettyCode);

How to Include Js File in Another Js File

How do I include a JavaScript file in another JavaScript file?

ES6 Modules

ECMAScript modules in browsers

Dynamic imports in browsers

Node.js require

AJAX Loading

Fetch Loading

jQuery Loading

Dynamic Script Loading

Detecting when the script has been executed

Source Code Merge/Preprocessing

Include a JS file directly in another?

How to include js file in another js file?

Include a JS file in another JS file with pure JS

Import functions from another js file. Javascript

how to import external js file when using bootstrap?

Importing an external js file into another external js file

Javascript - Issue passing object from one JS file to another JS file

How do I include a JavaScript file in another JavaScript file?

ES6 Modules

ECMAScript modules in browsers

Dynamic imports in browsers

Node.js require

AJAX Loading

Fetch Loading

jQuery Loading

Dynamic Script Loading

Detecting when the script has been executed

Source Code Merge/Preprocessing

Related Topics

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