elements
{ src: 'plugin/highlight/highlight.js', async: true, callback: function() { hljs.initHighlightingOnLoad(); } },
// Zoom in and out with Alt+click
{ src: 'plugin/zoom-js/zoom.js', async: true },
// Speaker notes
{ src: 'plugin/notes/notes.js', async: true },
// MathJax
{ src: 'plugin/math/math.js', async: true }
]
});
```
You can add your own extensions using the same syntax. The following properties are available for each dependency object:
- **src**: Path to the script to load
- **async**: [optional] Flags if the script should load after reveal.js has started, defaults to false
- **callback**: [optional] Function to execute when the script has loaded
- **condition**: [optional] Function which must return true for the script to be loaded
### Ready Event
A 'ready' event is fired when reveal.js has loaded all non-async dependencies and is ready to start navigating. To check if reveal.js is already 'ready' you can call `Reveal.isReady()`.
```javascript
Reveal.addEventListener( 'ready', function( event ) {
// event.currentSlide, event.indexh, event.indexv
} );
```
### Auto-sliding
Presentations can be configured to progress through slides automatically, without any user input. To enable this you will need to tell the framework how many milliseconds it should wait between slides:
```javascript
// Slide every five seconds
Reveal.configure({
autoSlide: 5000
});
```
When this is turned on a control element will appear that enables users to pause and resume auto-sliding. Alternatively, sliding can be paused or resumed by pressing »a« on the keyboard. Sliding is paused automatically as soon as the user starts navigating. You can disable these controls by specifying ```autoSlideStoppable: false``` in your reveal.js config.
You can also override the slide duration for individual slides and fragments by using the ```data-autoslide``` attribute:
```html
After 2 seconds the first fragment will be shown.
After 10 seconds the next fragment will be shown.
Now, the fragment is displayed for 2 seconds before the next slide is shown.
```
To override the method used for navigation when auto-sliding, you can specify the ```autoSlideMethod``` setting. To only navigate along the top layer and ignore vertical slides, set this to ```Reveal.navigateRight```.
Whenever the auto-slide mode is resumed or paused the ```autoslideresumed``` and ```autoslidepaused``` events are fired.
### Keyboard Bindings
If you're unhappy with any of the default keyboard bindings you can override them using the ```keyboard``` config option:
```javascript
Reveal.configure({
keyboard: {
13: 'next', // go to the next slide when the ENTER key is pressed
27: function() {}, // do something custom when ESC is pressed
32: null // don't do anything when SPACE is pressed (i.e. disable a reveal.js default binding)
}
});
```
### Touch Navigation
You can swipe to navigate through a presentation on any touch-enabled device. Horizontal swipes change between horizontal slides, vertical swipes change between vertical slides. If you wish to disable this you can set the `touch` config option to false when initializing reveal.js.
If there's some part of your content that needs to remain accessible to touch events you'll need to highlight this by adding a `data-prevent-swipe` attribute to the element. One common example where this is useful is elements that need to be scrolled.
### Lazy Loading
When working on presentation with a lot of media or iframe content it's important to load lazily. Lazy loading means that reveal.js will only load content for the few slides nearest to the current slide. The number of slides that are preloaded is determined by the `viewDistance` configuration option.
To enable lazy loading all you need to do is change your "src" attributes to "data-src" as shown below. This is supported for image, video, audio and iframe elements. Lazy loaded iframes will also unload when the containing slide is no longer visible.
```html
![]()
```
### API
The ``Reveal`` object exposes a JavaScript API for controlling navigation and reading state:
```javascript
// Navigation
Reveal.slide( indexh, indexv, indexf );
Reveal.left();
Reveal.right();
Reveal.up();
Reveal.down();
Reveal.prev();
Reveal.next();
Reveal.prevFragment();
Reveal.nextFragment();
// Randomize the order of slides
Reveal.shuffle();
// Toggle presentation states, optionally pass true/false to force on/off
Reveal.toggleOverview();
Reveal.togglePause();
Reveal.toggleAutoSlide();
// Change a config value at runtime
Reveal.configure({ controls: true });
// Returns the present configuration options
Reveal.getConfig();
// Fetch the current scale of the presentation
Reveal.getScale();
// Retrieves the previous and current slide elements
Reveal.getPreviousSlide();
Reveal.getCurrentSlide();
Reveal.getIndices(); // { h: 0, v: 0 } }
Reveal.getProgress(); // 0-1
Reveal.getTotalSlides();
// Returns the speaker notes for the current slide
Reveal.getSlideNotes();
// State checks
Reveal.isFirstSlide();
Reveal.isLastSlide();
Reveal.isOverview();
Reveal.isPaused();
Reveal.isAutoSliding();
```
### Slide Changed Event
A 'slidechanged' event is fired each time the slide is changed (regardless of state). The event object holds the index values of the current slide as well as a reference to the previous and current slide HTML nodes.
Some libraries, like MathJax (see [#226](https://github.com/hakimel/reveal.js/issues/226#issuecomment-10261609)), get confused by the transforms and display states of slides. Often times, this can be fixed by calling their update or render function from this callback.
```javascript
Reveal.addEventListener( 'slidechanged', function( event ) {
// event.previousSlide, event.currentSlide, event.indexh, event.indexv
} );
```
### Presentation State
The presentation's current state can be fetched by using the `getState` method. A state object contains all of the information required to put the presentation back as it was when `getState` was first called. Sort of like a snapshot. It's a simple object that can easily be stringified and persisted or sent over the wire.
```javascript
Reveal.slide( 1 );
// we're on slide 1
var state = Reveal.getState();
Reveal.slide( 3 );
// we're on slide 3
Reveal.setState( state );
// we're back on slide 1
```
### Slide States
If you set ``data-state="somestate"`` on a slide ````, "somestate" will be applied as a class on the document element when that slide is opened. This allows you to apply broad style changes to the page based on the active slide.
Furthermore you can also listen to these changes in state via JavaScript:
```javascript
Reveal.addEventListener( 'somestate', function() {
// TODO: Sprinkle magic
}, false );
```
### Slide Backgrounds
Slides are contained within a limited portion of the screen by default to allow them to fit any display and scale uniformly. You can apply full page backgrounds outside of the slide area by adding a ```data-background``` attribute to your `````` elements. Four different types of backgrounds are supported: color, image, video and iframe. Below are a few examples.
```html
All CSS color formats are supported, like rgba() or hsl().
This slide will have a full-size background image.
This background image will be sized to 100px and repeated.
Video. Multiple sources can be defined using a comma separated list. Video will loop when the data-background-video-loop attribute is provided and can be muted with the data-background-video-muted attribute.
Embeds a web page as a background. Note that the page won't be interactive.
```
Backgrounds transition using a fade animation by default. This can be changed to a linear sliding transition by passing ```backgroundTransition: 'slide'``` to the ```Reveal.initialize()``` call. Alternatively you can set ```data-background-transition``` on any section with a background to override that specific transition.
### Parallax Background
If you want to use a parallax scrolling background, set the first two config properties below when initializing reveal.js (the other two are optional).
```javascript
Reveal.initialize({
// Parallax background image
parallaxBackgroundImage: '', // e.g. "https://s3.amazonaws.com/hakim-static/reveal-js/reveal-parallax-1.jpg"
// Parallax background size
parallaxBackgroundSize: '', // CSS syntax, e.g. "2100px 900px" - currently only pixels are supported (don't use % or auto)
// Number of pixels to move the parallax background per slide
// - Calculated automatically unless specified
// - Set to 0 to disable movement along an axis
parallaxBackgroundHorizontal: 200,
parallaxBackgroundVertical: 50
});
```
Make sure that the background size is much bigger than screen size to allow for some scrolling. [View example](http://lab.hakim.se/reveal-js/?parallaxBackgroundImage=https%3A%2F%2Fs3.amazonaws.com%2Fhakim-static%2Freveal-js%2Freveal-parallax-1.jpg¶llaxBackgroundSize=2100px%20900px).
### Slide Transitions
The global presentation transition is set using the ```transition``` config value. You can override the global transition for a specific slide by using the ```data-transition``` attribute:
```html
This slide will override the presentation transition and zoom!
Choose from three transition speeds: default, fast or slow!
```
You can also use different in and out transitions for the same slide:
```html
The train goes on …
and on …
and stops.
(Passengers entering and leaving)
And it starts again.
```
### Internal links
It's easy to link between slides. The first example below targets the index of another slide whereas the second targets a slide with an ID attribute (``````):
```html
Link
Link
```
You can also add relative navigation links, similar to the built in reveal.js controls, by appending one of the following classes on any element. Note that each element is automatically given an ```enabled``` class when it's a valid navigation route based on the current slide.
```html
```
### Fragments
Fragments are used to highlight individual elements on a slide. Every element with the class ```fragment``` will be stepped through before moving on to the next slide. Here's an example: http://lab.hakim.se/reveal-js/#/fragments
The default fragment style is to start out invisible and fade in. This style can be changed by appending a different class to the fragment:
```html
grow
shrink
fade-out
fade-up (also down, left and right!)
visible only once
blue only once
highlight-red
highlight-green
highlight-blue
```
Multiple fragments can be applied to the same element sequentially by wrapping it, this will fade in the text on the first step and fade it back out on the second.
```html
I'll fade in, then out
```
The display order of fragments can be controlled using the ```data-fragment-index``` attribute.
```html
Appears last
Appears first
Appears second
```
### Fragment events
When a slide fragment is either shown or hidden reveal.js will dispatch an event.
Some libraries, like MathJax (see #505), get confused by the initially hidden fragment elements. Often times this can be fixed by calling their update or render function from this callback.
```javascript
Reveal.addEventListener( 'fragmentshown', function( event ) {
// event.fragment = the fragment DOM element
} );
Reveal.addEventListener( 'fragmenthidden', function( event ) {
// event.fragment = the fragment DOM element
} );
```
### Code syntax highlighting
By default, Reveal is configured with [highlight.js](https://highlightjs.org/) for code syntax highlighting. Below is an example with clojure code that will be syntax highlighted. When the `data-trim` attribute is present, surrounding whitespace is automatically removed. HTML will be escaped by default. To avoid this, for example if you are using `` to call out a line of code, add the `data-noescape` attribute to the `` element.
```html
(def lazy-fib
(concat
[0 1]
((fn rfib [a b]
(lazy-cons (+ a b) (rfib b (+ a b)))) 0 1)))
```
### Slide number
If you would like to display the page number of the current slide you can do so using the ```slideNumber``` configuration value.
```javascript
// Shows the slide number using default formatting
Reveal.configure({ slideNumber: true });
// Slide number formatting can be configured using these variables:
// "h.v": horizontal . vertical slide number (default)
// "h/v": horizontal / vertical slide number
// "c": flattened slide number
// "c/t": flattened slide number / total slides
Reveal.configure({ slideNumber: 'c/t' });
```
### Overview mode
Press "Esc" or "o" keys to toggle the overview mode on and off. While you're in this mode, you can still navigate between slides,
as if you were at 1,000 feet above your presentation. The overview mode comes with a few API hooks:
```javascript
Reveal.addEventListener( 'overviewshown', function( event ) { /* ... */ } );
Reveal.addEventListener( 'overviewhidden', function( event ) { /* ... */ } );
// Toggle the overview mode programmatically
Reveal.toggleOverview();
```
### Fullscreen mode
Just press »F« on your keyboard to show your presentation in fullscreen mode. Press the »ESC« key to exit fullscreen mode.
### Embedded media
Embedded HTML5 ` 