versions/0.2.2/oj.js
function _e(fn, msg){
    msg = _d(msg, fn, '')
    fn = _d(fn, 0)
    var pfx = "oj: "
    if (fn)
      pfx = "oj." + fn + ": "
    throw new Error(pfx + msg)
  }
function _e(fn, msg){
    msg = _d(msg, fn, '')
    fn = _d(fn, 0)
    var pfx = "oj: "
    if (fn)
      pfx = "oj." + fn + ": "
    throw new Error(pfx + msg)
  }
_e: error by throwing msg with optional fn name