Unlock Web Audio in iOS 9 Safari

unlock.js

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) {
    usingWebAudio = false;
}

// context state at this time is `undefined` in iOS8 Safari
if (usingWebAudio && ctx.state === 'suspended') {
  var resume = function () {
    ctx.resume();

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

  document.body.addEventListener('touchend', resume, false);
}

on iOS 11 it seems like the state turns into suspended every time you close safari. I had to listen for ctx.onstatechange and apply this trick again every time the state becomes suspended

Another note: I've just had all these problems and it still didn't work.

The user cannot be in Silent mode. Even if regular music and videos play with audio, webkitAudio will not.

So annoying