WebAudio API Polyfill for Safari Browsers

webaudio.polyfill.js

/**
 * Safari does handle web audio a bit different.
 *
 * Original found at
 *    https://gist.github.com/laziel/7aefabe99ee57b16081c
 *
 * Modified by Ikaros Kappler
 * @date 2017-11-15
 **/

function webaudioPolyfill( callback ) {
    var ctx = null, usingWebAudio = true;

    try {
      if (typeof AudioContext !== 'undefined') {
          ctx = new AudioContext();
      } else if (typeof webkitAudioContext !== 'undefined') {
          ctx = new webkitAudioContext();
      } else {
          usingWebAudio = false;
      }
    } catch(e) {
        console.log( e );
        usingWebAudio = false;
    }

    // context state at this time is `undefined` in iOS8 Safari
    if( usingWebAudio ) {
      var eventCalled = false;
      if( ctx.state === 'suspended') {
        console.log( 'web audio context is suspended!' );
        var resume = function () {
          console.log( 'resuming web audio context ...' );
          ctx.resume().then( function() { if( !eventCalled ) callback(ctx); eventCalled = true; } );

          setTimeout(function () {
            if (ctx.state === 'running') {
              document.body.removeEventListener('touchend', resume, false);
            }
          }, 0);
          
        };

        document.body.addEventListener('touchend', resume, false);
        ctx.resume().then( function() { if( !eventCalled ) callback(ctx); eventCalled = true; } );
      } else {
        callback(ctx);
      }
    }
}