vivus.js

Demo available on http://maxwellito.github.io/vivus

Vivus is a lightweight JavaScript class (with no dependencies) that allows you to animate SVGs, giving them the appearence of being drawn. There are a variety of different animations available, as well as the option to create a custom script to draw your SVG in whatever way you like.

Available via Bower: bower install vivus or via jsDelivr CDN: //cdn.jsdelivr.net/vivus/0.1.2/vivus.min.js

Animations

On the following images, the pink color represents the duration value, and the blue one is for delay value.

Delayed

Every path element is drawn at the same time with a small delay at the start. This is currently the default animation.

Async

Each line is drawn asynchronously. They all start and finish at the same time, hence the name async.

OneByOne

Each path element is drawn one after the other. This animation gives the best impression of live drawing. The duration for each line depends on their length to make a constant drawing speed.

Principles

To get this effect, the script uses the CSS property strokeDashoffset. This property manages the stroke offset on every line of the SVG. Now, all we have to do is add some JavaScript to update this value progressively and the magic begins.

However, there's a problem with this. The strokeDashoffset property is only available on the path elements. This is an issue because in an SVG there are a lot of elements such as circle, rect, line and polyline which will break the animation. So to fix this, there is another class available in the repo called pathformer. It's made for transforming all objects of your SVG into path elements to be able to use strokeDashoffset and animate your SVGs.

The animation always draws elements in the same order as they are defined in the SVG tag.

There are few conditions that your SVG must meet:

• All elements must have a stroke property and cannot be filled. This is because the animation only looks to progressively draw strokes and will not check for filled colours. For example: fill: "none"; stroke: "#FFF";

• You shoud avoid creating any hidden path elements in your SVG. Vivus considers them all eligible to be animated, so it is advised to remove them before playing with it. If they are not removed the animation might not achieve the desired effect, with blank areas and gaps appearing.

The code is inspired from other repositories. The drawer is inspired from the excellent Codrops about the post SVG Drawing Animation (if you don't know this website, get ready to have your mind blown). Then for the pathformer, there is a lot of work from SVGPathConverter by Waest.

Usage

As I said, no dependencies here. All you need to do is include the scripts.

new Vivus('my-svg-id', {type: 'delayed', duration: 200}, myCallback);

The Vivus constructor asks for 3 parameters:

• The ID of the SVG to animate (or the DOM element)
• Option object (described in the following)
• Callback to call at the end of the animation (optional)

The option object must respect the following structure :

• type (string) defines what kind of animation will be used: delayed, async, oneByOne or script
• duration (integer) animation duration, in frames
• start (string) defines how to trigger the animation
  • inViewport once the SVG is in the viewport
  • manual gives you the freedom to call draw method to start
  • autostart makes it start right now
• delay (integer) time between the drawing of first and last path, in frames (only for delayed animations)
• dashGap (integer) whitespace extra margin between dashes. The default value is 2. Increase it in case of glitches at the initial state of the animation
• forceRender (boolean) force the browser to re-render all updated path items. By default, the value is true on IE only. (check the 'troubleshoot' section for more details)
• selfDestroy (boolean) removes all extra styling on the SVG, and leaves it as original

The Vivus object has 3 control methods:

• play(speed) Plays the animation with the speed given in parameter. This value can be negative to go backward, between 0 and 1 to go slowly, or superior to 1 to go fast. By default the value is 1.
• stop() Stops the animation.
• reset() Reinitialises the SVG to the original state: undraw.

These control methods return the object so you can chain the actions.

var myVivus = new Vivus('my-svg-id');
myVivus
  .stop()
  .reset()
  .play(2)

Scenarize

This feature allows you to script the animation of your SVG. For this, the custom values will be set directly in the DOM of the SVG.

scenario

This type is easier to understand, but longer to implement. You just have to define the start and duration of each element with data-start and data-duration attributes. If it is missing, it will use the default value given to the constructor. The best part of this type is the flexibility it provides. You don't have to respect the order/stack of the SVG and you can start with the last element, then continue with the first to finish with all the rest at the same time.

You will then have to define custom rules for each element in your SVG via extra attributes in your SVG DOM :

• data-start (integer) time when the animation must start, in frames
• data-duration (integer) animation duration of this path, in frames

<svg>
  <path data-start="0" data-duration="10" .../>
  <path data-start="20" data-duration="10" .../>
  <path data-start="20" data-duration="20" .../>
  <path data-start="0" data-duration="30" .../>
</svg>

scenario-sync

It's not the sexiest code ever, but it's quite flexible. In addition to this, the behaviour is fairly different. By using this animation type, the default behaviour is the same as oneByOne. However, you can define some properties on a specific path item such as the duration, the delay to start (from the end of the previous path) and if it should be played asynchronously.

• data-delay (integer) time between the end of the animation of the previous path and the start of the current path, in frames
• data-duration (integer) duration of this path animation, in frames
• data-async (no value required) make the drawing of this path asynchronous. It means the next path will start at the same time. If a path does not have an attribute for duration or delay then the default values, set in the options, will be used.

Example: here is a simple SVG containing 5 elements. With the following options {duration: 20, delay: 0}, we should get this timeline

This looks like 'oneByOne' animation, synchronous mode. But to make it a bit custom, here is what I can do:

<svg>
	<path data-duration="10" .../>
	<path data-delay="10" data-async .../>
	<path data-delay="15" .../>
	<path data-duration="10" data-delay="45" data-async .../>
	<path data-duration="50" data-delay="5" .../>
</svg>

This scenario should give us

I'm sorry if it does not look very sexy, and it's not really easy to use. I'm happy to make any changes, as long as the idea sounds interesting. Post an issue and I'll be very happy to talk about it!

Development

To make it simpler a gulp file is set up to automise minifying, JShint and tests. If you have never used Gulp before this is a good opportunity. To use it, you need to install NodeJS first then run sudo npm install -g gulp.

To start, you will need to install the repo dependencies:

$ npm install

Then you can run Gulp with one of the following tasks:

• distrib make the build (generate dist/vivus.js and dist/vivus.min.js)
• lint run JShint on the source files
• test run Karma
• develop keep watching your files, if any change is applied, Gulp will run the task(s) related to it.

Troubleshoot

Internet Explorer

Some SVG werent't working at all. The only solution found was to clone and replace each updated path element. Of course this solution requires more resources and a lot of DOM manipulation, but it will give a smooth animation like other browsers. This fallback is only applied on Internet Explorer (all versions), and can be disabled via the option forceRender.

Replacing each updated path by a clone was the only way to force IE to re-render the SVG. On some SVGs this trick is not necessary, but IE can be a bit tricky with this. If you're worried about performances, I would recommend you to check if your SVG works correctly by disabling the forceRender option. If it works correctly on IE, then keep it like this.

By default, forceRender is true on Internet Explorer only.

Firefox

For Firefox users, you might encounter some glitches depending on your SVG and browser version. On versions before 36, there is a problem to retrieve path length via getTotalLength method. Returning 174321516544 instead of 209 (I'm not exaggerating, this comes from a real case), messing up the entire animation treatment. Unfortunately, there's nothing that this library can do, this is due to Firefox. I hope to find a workaround, but at the moment I can only recommend that you test your animation on previous versions of Firefox.

Debug

For an easier debug have a look to the attribute map of your Vivus object. This contains the mapping of your animation. If you're using Google Chrome, I recommend you use console.table to get a nice output of the array which will make your debug easier.

var logo = new Vivus('myLogo', {type: 'scenario-sync'});

// The property 'map' contain all the SVG mapping
console.table(logo.map);