Impetus.js

Add momentum to anything. It's like iScroll, except not for scrolling. Supports mouse and touch events.

Check out the demos on the home page.

Impetus will probably never support anything other than simple momentum. If you need scrolling or touch carousels or anything like that, this probably isn't the tool you're looking for.

Usage

var myImpetus = new Impetus({
    source: myNode,
    update: function(x, y) {
        // whatever you want to do with the values
    }
});

You give it an area to listen to for touch or mouse events, and it gives you the x and y values with some momentum.

Impetus will register itself as an AMD module if it's available.

Constructor Options

<table> <thead> <tr> <th></th> <th scope="col">Type</th> <th scope="col">Default</th> <th scope="col">Description</th> </tr> </thead> <tbody> <tr> <th scope="row" align="left"><code>source</code></th> <td><code>HTMLElement</code>|<code>String</code></td> <td>document</td> <td>Element reference or query string for the target on which to listen for movement.</td> </tr> <tr> <th scope="row" align="left"><code>update</code> (required)</th> <td><code>function(x, y)</code></td> <td>-</td> <td>This function will be called with the updated <var>x</var> and <var>y</var> values.</td> </tr> <tr> <th scope="row" align="left"><code>multiplier</code></th> <td><code>Number</code></td> <td><code>1</code></td> <td>The relationship between the input and output values.</td> </tr> <tr> <th scope="row" align="left"><code>friction</code></th> <td><code>Number</code></td> <td><code>0.92</code></td> <td>Rate at which values slow down after you let go.</td> </tr> <tr> <th scope="row" align="left"><code>initialValues</code></th> <td><code>[Number, Number]</code></td> <td><code>[0, 0]</code></td> <td>Array of initial <var>x</var> and <var>y</var> values.</td> </tr> <tr> <th scope="row" align="left"><code>boundX</code></th> <td><code>[Number, Number]</code></td> <td>-</td> <td>Array of low and high values. <var>x</var>-values will remain within these bounds.</td> </tr> <tr> <th scope="row" align="left"><code>boundY</code></th> <td><code>[Number, Number]</code></td> <td>-</td> <td>Array of low and high values. <var>y</var>-values will remain within these bounds.</td> </tr> <tr> <th scope="row" align="left"><code>bounce</code></th> <td><code>Boolean</code></td> <td><code>true</code></td> <td>Whether to stretch and rebound values when pulled outside the bounds.</td> </tr> </tbody> </table>

Methods

<table> <thead> <tr> <th></th> <th scope="col">Description</th> </tr> </thead> <tbody> <tr> <th scope="row" align="left"><code>.pause()</code></th> <td>Disable movement processing.</td> </tr> <tr> <th scope="row" align="left"><code>.resume()</code></th> <td>Re-enable movement processing.</td> </tr> <tr> <th scope="row" align="left"><code>.setMultiplier( &lt;number&gt; )</code></th> <td>Adjust the <var>multiplier</var> in flight.</td> </tr> <tr> <th scope="row" align="left"><code>.setValues( &lt;number&gt; , &lt;number&gt; )</code></th> <td>Adjust the current <var>x</var> and <var>y</var> output values.</td> </tr> <tr> <th scope="row" align="left"><code>.setBoundX( &lt;number[2]&gt; )</code></th> <td>Adjust the X bound</td> </tr> <tr> <th scope="row" align="left"><code>.setBoundY( &lt;number[2]&gt; )</code></th> <td>Adjust the Y bound</td> </tr> <tr> <th scope="row" align="left"><code>.destroy()</code></th> <td> This will remove the previous event listeners. Returns null so you can use it to destroy your variable if you wish, i.e. <code>instance = instance.destroy()</code> </td> </tr> </tbody> </table>

Browser Support

Chrome, Firefox, Safari, Opera, IE 9+, iOS, Android. Support for IE 8 can be achieved by adding a polyfill for addEventListener.