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The Player & Driver

HTML exports come with two important files – Player.js and Driver.js.


The Driver is a class that registers with the UI on the main index page, allowing a user to play / pause and drag a slider to drive the animation.

The Driver is a simple extension of Player.js, the main class that actually handles the playback control and setup of your animations.


The Player class is responsible for setting up animations, and has all the playback functionality you’ll need to work with your animations.

You can find the file in the js folder of any HTML export.

Location of player.js in the Move project, from the intro.flow file.

Have a look at the code for Player.js

Working with the Player

The interface for the player is pretty straightforward – it has the same functions as the driver class.


This is the constructor for creating a player:

constructor(timeline, timerID, loop, delay).

You need to pass:

  1. the Timeline class (e.g. SquareTimeline)
  2. the timerID associated with the animation you’re creating the player for
  3. bool whether to loop the animation
  4. adds a delay time (in milliseconds) at the END of an animation

An example of creating a non-looping animation that starts right away is:

var squarePlayer = new Player(SquareTimeline, 'SquareTimer', false, 0)


You can set and get the current time of a player:

player.currentTime = 0
player.currentTime = 100

Players track time in milliseconds


To start an animation from it’s current time:


You can check if a player is currently playing:



You can pause a player:


Pausing simply stops all animations at the current time.


You can stop a player:


Stopping will also set the player’s currentTime to 0


The driver is responsible for interfacing with UI elements on an html page. It is an extension of a player and therefore shares the same playback functionality as you saw above.

  • a play/pause button
  • a loop button
  • a slider
  • a time label

You can find the file in the js folder of any HTML export.

Location of driver.js in the Move project, from the intro.flow file.

Have a look at the code for Driver.js

Working with the Driver

The driver has all the same playback commands as the player.


The major difference between the driver and player is the constructor, where the driver requires you pass it the ids for the interface elements associated with it.

Driver(timeline, loopButtonID, playButtonID, sliderID, timeLabelID, timerID)

You need to pass:

  1. the Timeline class (e.g. SquareTimeline)
  2. the id for the loopButton tag
  3. the id for the playButton tag
  4. the id for the slider tag
  5. the id for the timeLabel tag
  6. the id for the timer tag

You should pass unique ids to the for interface elements to the driver.

Here’s an example from the move timeline in the intro.flow file:

new Driver(Move, 'loopButton-move', 'playPauseButton-move', 'slider-move', 'timeLabel-move', 'timer-move')


The driver requires a DOM in order to be initialized. As you may have guessed from the constructor, there are 5 main elements that the standard driver requires during initialization.

Here’s what the driver looks like:

<div class="playback">
  <div class="slider">
    <input type="range" min="0" max="1" step="0.001" value="0.0" id="slider-wordmark" />
  <div class="controls">
    <div class="playPauseLoop">
      <div class="playPauseContainer loop">
        <input type='checkbox' id="loopButton-wordmark">
        <label for="loopButton-wordmark" class="loopLabel" id="loopLabel" />
      <div class="playPauseContainer">
        <input type='checkbox' id="playPauseButton-wordmark">
        <label for="playPauseButton-wordmark" class="playPauseLabel" id="playPauseLabel" />
      <div class="playPauseContainer">
        <div class="time" id="timeLabel-wordmark">0 s</div>


During the initialization of a driver, the following function gets called:

createControlFunctions() { ... }

This function is reponsible for linking the driver directly to the UI in your dom.

Styling the Driver

The driver also requires its own CSS. The standard export looks like this:

A pretty set of playback controls.
Location of driver.css in the Move project, from the intro.flow file.

Have a look at the code for Driver.css

Triggering Events

You can trigger events to occur when animations finish by overriding or re-writing the createOnFinishCallback() function. This works for both the driver and player classes.


This method currently looks like the following:

createOnFinishCallback() {
  if (this.timingAnimation == null) {
  this.timingAnimation.onfinish = () => {
    if (this.loop == true) {
      this.currentTime = 0
    } else {

To add your own function call to be triggered when an animation ends.

() => {
  if (this.loop == true) {
    this.currentTime = 0
  } else {

This callback creation function gets executed at the end of the player’s constructor.

The callback actually tracks the animation attached to the timer because its duration represents the entire duration of the set of animantions laced throughout svgs and other elements in your timeline

Replacing the Driver

By default, the page you export from Flow uses a driver. Here are a few simple steps to remove and replace it with a player.

Driver.js Code

This is the code for the Move timeline:

<script type="text/javascript">
  document.driverMove = new Driver(Move, 'loopButton-move', 'playPauseButton-move', 'slider-move', 'timeLabel-move', 'timer-move')
  document.driverMove.currentTime = 0
  document.addEventListener('keyup', function (event) {
    if (event.defaultPrevented) {

    var key = event.key || event.keyCode;

    if (key === 'Space' || key === " " || key === 32) {
      let button = document.driverMove.playPauseButton
      button.checked = !button.checked

Replace the above with…

<script src="js/player.js"></script>
<script type="text/javascript">
  document.playerMove = new Player(Timeline, 'timer-move', true, 0)
  document.playerMove.currentTime = 0

Driver UI Code

Remove the driver UI by deleting the playback div:

<div class="playback">

Driver Files

You can also delete:

  • js > driver.js
  • css > driver.css

Driving Animations

To hook up your animations to user input, sliders, or events, simply bind whatever it is you’re tracking to the currentTime of the animation.

For example, the standard driver binds the animation to the slider like so:

this.slider.oninput = () => {

  var newTime = this.slider.value * this.duration

  var newTime = Math.min(newTime, this.duration - 1)
  this.currentTime = newTime


Multiple Animations

To have multiple animations on a page requires every player – or driver – to have a unique timer.

The current HTML template exports each timer with its own unique id, which is defined by the name of the timeline you’re exporting.

For example, in the Move timeline from the intro.flow file, the timer id looks like this:

<div id="timer-move"></div>


…you want multiple animations all driven by the same timer, or driver UI.

Multiple Animation Example

Here is an example that we cooked up for you.

The following download contains a Sketch and a Flow file as well as a modified export from Flow, which has 4 animations running independently using players instead of drivers.

Multi Animation Example

Remember to hit up our Slack Channel if you have any questions.

background Made with Flow.
underscore Made with Flow.
line2 Made with Flow.
line1 Made with Flow.
circle Made with Flow.
hit Made with Flow.

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