src/rules.js
function(passes, message) {
    this.passes = (passes === undefined || passes === true);
    this._customMessage = message;
    this.callback(this.passes, message);
  }
function(passes, message) {
    this.passes = (passes === undefined || passes === true);
    this._customMessage = message;
    this.callback(this.passes, message);
  }
function ( passes , message ) { this . passes = ( passes === undefined || passes === true ) ; this . _customMessage = message ; this . callback ( this . passes , message ) ; }
Set the async callback response

@param  {boolean|undefined} passes  Whether validation passed
@param  {string|undefined} message Custom error message
@return {void}
Set the async callback response