Modernizr/Modernizr

/*!
{
  "name": "Audio Autoplay",
  "property": "audioautoplay",
  "authors": ["Jordy van Dortmont"],
  "tags": ["audio"],
  "async": true
}
!*/
/* DOC
Checks for support of the autoplay attribute of the audio element.
*/
define(['Modernizr', 'addTest', 'docElement', 'createElement', 'test/audio/audio'], function(Modernizr, addTest, docElement, createElement) {

  Modernizr.addAsyncTest(function() {
    var timeout;
    var waitTime = 200;
    var retries = 5;
    var currentTry = 0;
    var elem = createElement('audio');
    var elemStyle = elem.style;

    function testAutoplay(arg) {
      currentTry++;
      clearTimeout(timeout);

      var result = arg && arg.type === 'playing' || elem.currentTime !== 0;

      if (!result && currentTry < retries) {
        // Detection can be flaky if the browser is slow, so lets retry in a little bit
        timeout = setTimeout(testAutoplay, waitTime);
        return;
      }

      elem.removeEventListener('playing', testAutoplay, false);
      addTest('audioautoplay', result);

      // Cleanup, but don't assume elem is still in the page -
      // an extension may already have removed it.
      if (elem.parentNode) {
        elem.parentNode.removeChild(elem);
      }
    }

    // Skip the test if audio itself, or the autoplay element on it isn't supported
    if (!Modernizr.audio || !('autoplay' in elem)) {
      addTest('audioautoplay', false);
      return;
    }

    elemStyle.position = 'absolute';
    elemStyle.height = 0;
    elemStyle.width = 0;

    try {
      if (Modernizr.audio.mp3) {
        elem.src = 'data:audio/mpeg;base64,/+MYxAAAAANIAUAAAASEEB/jwOFM/0MM/90b/+RhST//w4NFwOjf///PZu////9lns5GFDv//l9GlUIEEIAAAgIg8Ir/JGq3/+MYxDsLIj5QMYcoAP0dv9HIjUcH//yYSg+CIbkGP//8w0bLVjUP///3Z0x5QCAv/yLjwtGKTEFNRTMuOTeqqqqqqqqqqqqq/+MYxEkNmdJkUYc4AKqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq';
      }
      else if (Modernizr.audio.wav) {
        elem.src = 'data:audio/wav;base64,UklGRjQAAABXQVZFZm10IBAAAAABAAEAEAAAABAAAAABAAgAZGF0YRAAAAB/f39/f39/f39/f39/f39/';
      }
      else {
        addTest('audioautoplay', false);
        return;
      }
    }

    catch (e) {
      addTest('audioautoplay', false);
      return;
    }

    elem.setAttribute('autoplay', '');
    elemStyle.cssText = 'display:none';
    docElement.appendChild(elem);
    // Wait for the next tick to add the listener, otherwise the element may
    // not have time to play in high load situations (e.g. the test suite)
    setTimeout(function() {
      elem.addEventListener('playing', testAutoplay, false);
      timeout = setTimeout(testAutoplay, waitTime);
    }, 0);
  });
});