code: function checkRTCDataChannelState(key, value)
  {
    if(typeof value != 'string')
      throw SyntaxError(key+' param should be a String, not '+typeof value);
  
    if(!value.match('connecting|open|closing|closed'))
      throw SyntaxError(key+' param is not one of [connecting|open|closing|closed] ('+value+')');
  }
docs: Represents the state of the RTCDataChannel
  
  @typedef core/complexTypes.RTCDataChannelState
  
  @type {(connecting|open|closing|closed)}
   
  Checker for {@link module:core/complexTypes.RTCDataChannelState}
  
  @memberof module:core/complexTypes
  
  @param {external:String} key
  @param {module:core/complexTypes.RTCDataChannelState} value