A very simple script to watch for .js & .css files present in DOM
over AJAX and reload the page/CSS when changes are detected.
Just throw the watchem.min.js into your HTML and it starts watching your assets.
That simple!
At the bottom of you <body>, after all <script> tags add this:
```html
<script src="https://unpkg.com/watchem.js" async></script>
```
And that should be enough to automatically watch resources (JS & CSS & the page)
of this page.
For advanced configuration, you can call `watchem.setOption(name, value)`.
When `watchem` is loaded, it invokes `window.watchemInit(watchem)`:
```js
window.watchemInit = (watchem) => {
// These are the defaults:
watchem.setOption({
interval: 500, // Recheck/ping interval
reDOM: 5e3, // Recheck DOM interval
wDoc: true, // Watch this document change
wCSS: true, // Watch CSS change
wJS: true, // Watch JS change
noMin: true, // Ignore .min.js or .min.css
hostAlias: {}, // eg. { 'cdn.example.com': 'example.com', 'www.example.com': 'example.com' }
wHosts: [location.hostname], // Automatically watch JS & CSS only for these hostnames
// !!! CORS restrictions apply !!!
// Ping request methods
defMethod: 'HEAD',
altMethod: 'GET',
headers: { 'X-Requested-With': 'Watchem' },
});
};
```
You can stop the watcher from console
```js
watchem.stop(); // stops the watcher and remembers the state in localStorage
```
and start it later
```js
watchem.start();
```
You can add more files to watchem or exclude some by:
```js
var watchemToo = {
'/assets/someModule.js': true, // watch
'/assets/jquery.js': false, // don't watch
};
// Auto-invokes watchem.watch(window.watchemToo, true); at options.reDOM interval
window.watchemToo = watchemToo;
// or
watchem.watch(watchemToo, true);
// or
// External (to DOM) resources have lower priority (just a delay in watching)
watchem.watch(['/external/to/dom/file.js'], true);
```
### How it works
It makes `HEAD` (`options.defMethod`) requests to the server in the specified interval and compares
`ETag` or `Last-Modified` and `Content-Length` and `Content-Type` header with the stored value.
If server does not return any of the tracked headers, it makes
`GET` requests (`options.altMethod`) and compares the contents of the file.
Note that a `GET` request is more expensive than `HEAD`.
### When should I use it
I find it best suited for TDD / BDD and for designing using HTML & CSS.
I've built this script to automatically run [Jasmine](https://jasmine.github.io/)
specs inside a Chrome Extension on source files change
(do you know about [Karma](https://karma-runner.github.io/)?),
but it can be successfully used for any web app.
For advanced stuff I recommend [BrowserSync](https://browsersync.io/) (requires Node.js).
### Dependencies
Requires one of:
- [jAJAX](https://github.com/duzun/jAJAX)
- or [jQuery v1.5+](https://api.jquery.com/jquery.ajax/)
- or [Zepto v1.1+](http://zeptojs.com/#$.ajax) "callbacks" and "deferred" modules loaded
- or a custom method named `jajax` that looks like this one:
```js
window.jajax = (opt, suc, err) => {
return jQuery.ajax(opt).done(suc).fail(err);
};
```
If none of the above is found, it will try to load [unpkg.com/jajax.js](https://unpkg.com/jajax.js)
automatically.
### Browser Compatibility
I've tested it on **Google Chrome 39-47**, **Safari 5.1-9.0** and **Firefox 36-41** so far.
I don't know when I would need to use it in other browser, but PRs are welcome.
### Alternatives
- [Live.js](http://livejs.com/)
- [BrowserSync](https://browsersync.io/) (requires Node.js)
- [Live Reload](http://livereload.com/) (native app)
- [NppSync](https://github.com/duzun/NppSync) (for Notepad++ lovers)