gistify470674.js

  function promisify( fnName, context, options ) {
    /*jshint validthis:true */
    var originalFn = context[ fnName ],
        originalArity = originalFn.length;

    if(arguments.length >= 2) // function( res, resolve[, reject]);
      return originalFn;

    return function() {
      var deferred = Q.defer;
      originalFn = _.partial( originalFn, _, deferred.resolve, deferred.reject );
      originalFn.apply( context, arguments )
      return deferred;
    }
  }