LoadJS

LoadJS is a tiny async loader for modern browsers (961 bytes).

![CDNJS](https://cdnjs.com/libraries/loadjs)

Introduction

LoadJS is a tiny async loading library for modern browsers (IE9+). It has a simple yet powerful dependency management system that lets you fetch JavaScript, CSS and image files in parallel and execute code after the dependencies have been met. The recommended way to use LoadJS is to include the minified source code of loadjs.js in your <html> (possibly in the <head> tag) and then use the loadjs global to manage JavaScript dependencies after pageload.

LoadJS is based on the excellent $script library by Dustin Diaz. We kept the behavior of the library the same but we re-wrote the code from scratch to add support for success/error callbacks and to optimize the library for modern browsers. LoadJS is 961 bytes (minified + gzipped).

Here's an example of what you can do with LoadJS:

``html`

You can also use more advanced syntax for more options:`html`

The latest version of LoadJS can be found in the dist/directory in this repository: * https://cdn.rawgit.com/kubetail-org/loadjs/4.3.0/dist/loadjs.js (for development) * https://cdn.rawgit.com/kubetail-org/loadjs/4.3.0/dist/loadjs.min.js (for production)

It's also available from these public CDNs:

* UNPKG * https://unpkg.com/loadjs@4.3.0/dist/loadjs.js (for development) * https://unpkg.com/loadjs@4.3.0/dist/loadjs.min.js (for production) * CDNJS * https://cdnjs.cloudflare.com/ajax/libs/loadjs/4.3.0/loadjs.js (for development) * https://cdnjs.cloudflare.com/ajax/libs/loadjs/4.3.0/loadjs.min.js (for production)

You can also use it as a CJS or AMD module:

`bash $ npm install --save loadjs`

`javascript var loadjs = require('loadjs');

loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar');

loadjs.ready('foobar', function() { / foo.js & bar.js loaded / });`

`Browser Support`

* IE9+ (async: falsesupport only works in IE10+) * Opera 12+ * Safari 5+ * Chrome * Firefox * iOS 6+ * Android 4.4+

LoadJS also detects script load failures from AdBlock Plus and Ghostery in:

* Safari * Chrome

Note: LoadJS treats empty CSS files as load failures in IE9-11 and uses rel="preload" to load CSS files in Edge (to get around lack of support for onerror events on tags)

`Documentation`

1. Load a single file

`javascript loadjs('/path/to/foo.js', function() { / foo.js loaded / });`

1. Fetch files in parallel and load them asynchronously

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], function() { / foo.js and bar.js loaded / });`

1. Fetch JavaScript, CSS and image files

`javascript loadjs(['/path/to/foo.css', '/path/to/bar.png', 'path/to/thunk.js'], function() { / foo.css, bar.png and thunk.js loaded / });`

1. Force treat file as CSS stylesheet

`javascript loadjs(['css!/path/to/cssfile.custom'], function() { / cssfile.custom loaded as stylesheet / });`

1. Force treat file as image

`javascript loadjs(['img!/path/to/image.custom'], function() { / image.custom loaded / });`

1. Load JavaScript files as modules with non-module fallbacks (in browsers without module support)

`javascript loadjs(['module!/path/to/foo.js', 'nomodule!/path/to/bar.js'], function() { / foo.js loaded with type="module" in browsers with module support, skipped silently in browsers without / / bar.js loaded with type="text/javascript" in browsers without module support, skipped silently in browsers with / });`

1. Add a bundle id

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar', function() { / foo.js & bar.js loaded / });`

1. Use .ready() to define bundles and callbacks separately

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar');

loadjs.ready('foobar', function() { / foo.js & bar.js loaded / });`

1. Use multiple bundles in .ready() dependency lists

`javascript loadjs('/path/to/foo.js', 'foo'); loadjs(['/path/to/bar1.js', '/path/to/bar2.js'], 'bar');

loadjs.ready(['foo', 'bar'], function() { / foo.js & bar1.js & bar2.js loaded / });`

1. Chain .ready() together

`javascript loadjs('/path/to/foo.js', 'foo'); loadjs('/path/to/bar.js', 'bar');

loadjs .ready('foo', function() { / foo.js loaded / }) .ready('bar', function() { / bar.js loaded / });`

1. Use Promises to register callbacks

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], {returnPromise: true}) .then(function() { / foo.js & bar.js loaded / }) .catch(function(pathsNotFound) { / at least one didn't load / });`

1. Check if bundle has already been defined

`javascript if (!loadjs.isDefined('foobar')) { loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar', function() { / foo.js & bar.js loaded / }); }`

1. Fetch files in parallel and load them in series

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], { success: function() { / foo.js and bar.js loaded in series / }, async: false });`

1. Add an error callback

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar', { success: function() { / foo.js & bar.js loaded / }, error: function(pathsNotFound) { / at least one path didn't load / } });`

1. Retry files before calling the error callback

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar', { success: function() { / foo.js & bar.js loaded / }, error: function(pathsNotFound) { / at least one path didn't load / }, numRetries: 3 }); // NOTE: UsingnumRetries with async: falsecan cause files to load out-of-sync on retries`

1. Execute a callback before script tags are embedded

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], { success: function() {}, error: function(pathsNotFound) {}, before: function(path, scriptEl) { / called for each script node before being embedded / if (path === '/path/to/foo.js') scriptEl.crossOrigin = true; } });`

1. Bypass LoadJS default DOM insertion mechanism (DOM )

`javascript loadjs(['/path/to/foo.js'], { success: function() {}, error: function(pathsNotFound) {}, before: function(path, scriptEl) { document.body.appendChild(scriptEl); / returnfalse to bypass default DOM insertion mechanism / return false; } });`

1. Use bundle ids in error callback

`javascript loadjs('/path/to/foo.js', 'foo'); loadjs('/path/to/bar.js', 'bar'); loadjs(['/path/to/thunkor.js', '/path/to/thunky.js'], 'thunk');

// wait for multiple depdendencies loadjs.ready(['foo', 'bar', 'thunk'], { success: function() { // foo.js & bar.js & thunkor.js & thunky.js loaded }, error: function(depsNotFound) { if (depsNotFound.indexOf('foo') > -1) {}; // foo failed if (depsNotFound.indexOf('bar') > -1) {}; // bar failed if (depsNotFound.indexOf('thunk') > -1) {}; // thunk failed } });`1. Use .done() for more control

`javascript loadjs.ready(['dependency1', 'dependency2'], function() { / run code after dependencies have been met / });

function fn1() { loadjs.done('dependency1'); } function fn2() { loadjs.done('dependency2'); }`

1. Reset dependency trackers

`javascript loadjs.reset();`

1. Implement a require-like dependency manager

`javascript var bundles = { 'bundleA': ['/file1.js', '/file2.js'], 'bundleB': ['/file3.js', '/file4.js'] };

function require(bundleIds, callbackFn) { bundleIds.forEach(function(bundleId) { if (!loadjs.isDefined(bundleId)) loadjs(bundles[bundleId], bundleId); }); loadjs.ready(bundleIds, callbackFn); }

require(['bundleA'], function() { / bundleA loaded / }); require(['bundleB'], function() { / bundleB loaded / }); require(['bundleA', 'bundleB'], function() { / bundleA and bundleB loaded / });`

`Directory structure`


loadjs/
├── dist
│   ├── loadjs.js
│   ├── loadjs.min.js
│   └── loadjs.umd.js
├── examples
├── gulpfile.js
├── LICENSE.txt
├── package.json
├── README.md
├── src
│   └── loadjs.js
├── test
└── umd-templates

`Development Quickstart`

1. Install dependencies

* nodejs * npm * http-server (via npm)

1. Clone repository

`bash $ git clone git@github.com:kubetail-org/loadjs.git $ cd loadjs`

1. Install node dependencies using npm

`bash $ npm install`

1. Build examples

`bash $ npm run build-examples`

To view the examples you can use any static file server. To use the nodejs http-server module:

`bash $ npm install http-server $ npm run http-server -- -p 3000`

Then visit http://localhost:3000/examples

1. Build distribution files

`bash $ npm run build-dist`

The files will be located in the dist directory.

1. Run tests

To run the browser tests first build the loadjs library:

`bash $ npm run build-tests`

Then visit http://localhost:3000/test

1. Build all files

`bash $ npm run build-all``

LoadJS

LoadJS is a tiny async loader for modern browsers (961 bytes).

![CDNJS](https://cdnjs.com/libraries/loadjs)

Introduction

Here's an example of what you can do with LoadJS:

``html`

You can also use more advanced syntax for more options:`html`

It's also available from these public CDNs:

You can also use it as a CJS or AMD module:

`bash $ npm install --save loadjs`

`javascript var loadjs = require('loadjs');

loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar');

loadjs.ready('foobar', function() { / foo.js & bar.js loaded / });`

`Browser Support`

* IE9+ (async: falsesupport only works in IE10+) * Opera 12+ * Safari 5+ * Chrome * Firefox * iOS 6+ * Android 4.4+

LoadJS also detects script load failures from AdBlock Plus and Ghostery in:

* Safari * Chrome

Note: LoadJS treats empty CSS files as load failures in IE9-11 and uses rel="preload" to load CSS files in Edge (to get around lack of support for onerror events on tags)

`Documentation`

1. Load a single file

`javascript loadjs('/path/to/foo.js', function() { / foo.js loaded / });`

1. Fetch files in parallel and load them asynchronously

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], function() { / foo.js and bar.js loaded / });`

1. Fetch JavaScript, CSS and image files

`javascript loadjs(['/path/to/foo.css', '/path/to/bar.png', 'path/to/thunk.js'], function() { / foo.css, bar.png and thunk.js loaded / });`

1. Force treat file as CSS stylesheet

`javascript loadjs(['css!/path/to/cssfile.custom'], function() { / cssfile.custom loaded as stylesheet / });`

1. Force treat file as image

`javascript loadjs(['img!/path/to/image.custom'], function() { / image.custom loaded / });`

1. Load JavaScript files as modules with non-module fallbacks (in browsers without module support)

1. Add a bundle id

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar', function() { / foo.js & bar.js loaded / });`

1. Use .ready() to define bundles and callbacks separately

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar');

loadjs.ready('foobar', function() { / foo.js & bar.js loaded / });`

1. Use multiple bundles in .ready() dependency lists

`javascript loadjs('/path/to/foo.js', 'foo'); loadjs(['/path/to/bar1.js', '/path/to/bar2.js'], 'bar');

loadjs.ready(['foo', 'bar'], function() { / foo.js & bar1.js & bar2.js loaded / });`

1. Chain .ready() together

`javascript loadjs('/path/to/foo.js', 'foo'); loadjs('/path/to/bar.js', 'bar');

loadjs .ready('foo', function() { / foo.js loaded / }) .ready('bar', function() { / bar.js loaded / });`

1. Use Promises to register callbacks

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], {returnPromise: true}) .then(function() { / foo.js & bar.js loaded / }) .catch(function(pathsNotFound) { / at least one didn't load / });`

1. Check if bundle has already been defined

`javascript if (!loadjs.isDefined('foobar')) { loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar', function() { / foo.js & bar.js loaded / }); }`

1. Fetch files in parallel and load them in series

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], { success: function() { / foo.js and bar.js loaded in series / }, async: false });`

1. Add an error callback

`javascript loadjs(['/path/to/foo.js', '/path/to/bar.js'], 'foobar', { success: function() { / foo.js & bar.js loaded / }, error: function(pathsNotFound) { / at least one path didn't load / } });`

1. Retry files before calling the error callback

1. Execute a callback before script tags are embedded

1. Bypass LoadJS default DOM insertion mechanism (DOM )

1. Use bundle ids in error callback

`javascript loadjs('/path/to/foo.js', 'foo'); loadjs('/path/to/bar.js', 'bar'); loadjs(['/path/to/thunkor.js', '/path/to/thunky.js'], 'thunk');

`javascript loadjs.ready(['dependency1', 'dependency2'], function() { / run code after dependencies have been met / });

function fn1() { loadjs.done('dependency1'); } function fn2() { loadjs.done('dependency2'); }`

1. Reset dependency trackers

`javascript loadjs.reset();`

1. Implement a require-like dependency manager

`javascript var bundles = { 'bundleA': ['/file1.js', '/file2.js'], 'bundleB': ['/file3.js', '/file4.js'] };

function require(bundleIds, callbackFn) { bundleIds.forEach(function(bundleId) { if (!loadjs.isDefined(bundleId)) loadjs(bundles[bundleId], bundleId); }); loadjs.ready(bundleIds, callbackFn); }

require(['bundleA'], function() { / bundleA loaded / }); require(['bundleB'], function() { / bundleB loaded / }); require(['bundleA', 'bundleB'], function() { / bundleA and bundleB loaded / });`

`Directory structure`


loadjs/
├── dist
│   ├── loadjs.js
│   ├── loadjs.min.js
│   └── loadjs.umd.js
├── examples
├── gulpfile.js
├── LICENSE.txt
├── package.json
├── README.md
├── src
│   └── loadjs.js
├── test
└── umd-templates

`Development Quickstart`

1. Install dependencies

* nodejs * npm * http-server (via npm)

1. Clone repository

`bash $ git clone git@github.com:kubetail-org/loadjs.git $ cd loadjs`

1. Install node dependencies using npm

`bash $ npm install`

1. Build examples

`bash $ npm run build-examples`

To view the examples you can use any static file server. To use the nodejs http-server module:

`bash $ npm install http-server $ npm run http-server -- -p 3000`

Then visit http://localhost:3000/examples

1. Build distribution files

`bash $ npm run build-dist`

The files will be located in the dist directory.

1. Run tests

To run the browser tests first build the loadjs library:

`bash $ npm run build-tests`

Then visit http://localhost:3000/test

1. Build all files

`bash $ npm run build-all``