Question

Althought I pushed a parameter to getElementById I wonder from where is this ‘is null’ error coming from?

TypeError: document.getElementById(...) is null
[Break On This Error]   

document.getElementById(elmId).innerHTML = value;

Line 75  

In addition to this i wonder why title and time did not show unless I click one of these playlist pictures?

Answer 1

All these results in null:

document.getElementById('volume');
document.getElementById('bytesLoaded');
document.getElementById('startBytes');
document.getElementById('bytesTotal');

You need to do a null check in updateHTML like this:

function updateHTML(elmId, value) {
  var elem = document.getElementById(elmId);
  if(typeof elem !== 'undefined' && elem !== null) {
    elem.innerHTML = value;
  }
}