JavaScript drag and drop, resizing and multi-touch gestures with inertia and snapping for modern browsers (and also IE9+).

Features include:

• inertia and snapping
• multi-touch, simultaneous interactions
• cross browser and device, supporting the desktop and mobile versions of Chrome, Firefox and Opera as well as Internet Explorer 9+
• interaction with SVG elements
• being standalone and customizable
• not modifying the DOM except to change the cursor (but you can disable that)

Installation

• npm: npm install interactjs@next
• jsDelivr CDN: <script src="https://cdn.jsdelivr.net/npm/interactjs@next/dist/interact.min.js"></script>
• unpkg CDN: <script src="https://unpkg.com/interactjs@next/dist/interact.min.js"></script>
• Webjars SBT/Play 2: libraryDependencies ++= Seq("org.webjars.npm" % "interactjs" % version)
• Direct download the latest version: http://interactjs.io/#download
  • Rails 4 app development (using Rails Asset Pipeline)
    • Download the file interact.js (development version) into a new sub-directory: vendor/assets/javascripts/interact
    • Add //= require interact/interact in app/assets/javascripts/application.js (above //= require_tree .)
    • Restart the Rails server

Typescript definitions

The project is written in Typescript and the npm package includes the type definitions, but if you need the typings alone, you can install them with:

npm install --save-dev @interactjs/types

Documentation

http://interactjs.io/docs

Example

var pixelSize = 16;

interact('.rainbow-pixel-canvas')
  .origin('self')
  .draggable({
    modifiers: [{
      // snap to the corners of a grid
      type: 'snap',
      targets: [
        interact.snappers.grid({ x: pixelSize, y: pixelSize }),
      ],
    }],
  })
  // draw colored squares on move
  .on('dragmove', function (event) {
    var context = event.target.getContext('2d'),
        // calculate the angle of the drag direction
        dragAngle = 180 * Math.atan2(event.dx, event.dy) / Math.PI;

    // set color based on drag angle and speed
    context.fillStyle = 'hsl(' + dragAngle + ', 86%, '
                        + (30 + Math.min(event.speed / 1000, 1) * 50) + '%)';

    // draw squares
    context.fillRect(event.pageX - pixelSize / 2, event.pageY - pixelSize / 2,
                     pixelSize, pixelSize);
  })
  // clear the canvas on doubletap
  .on('doubletap', function (event) {
    var context = event.target.getContext('2d');

    context.clearRect(0, 0, context.canvas.width, context.canvas.height);
  });

  function resizeCanvases () {
    [].forEach.call(document.querySelectorAll('.rainbow-pixel-canvas'), function (canvas) {
      canvas.width = document.body.clientWidth;
      canvas.height = window.innerHeight * 0.7;
    });
  }

  // interact.js can also add DOM event listeners
  interact(document).on('DOMContentLoaded', resizeCanvases);
  interact(window).on('resize', resizeCanvases);

See the above code in action at https://codepen.io/taye/pen/tCKAm

License

interact.js is released under the MIT License.