Convert SharePoint JSOM's ExecuteQueryAsync to Promise in the Prototype

Today's blog is about adding an additional method to SharePoint JavaScript Object Model (JSOM)'s ClientContext object, so we can use it directly like a promise.

I call it "executeQuery" (instead of executeQueryAsync)

Wrapper with jQuery's $.Deferred

SP.ClientContext.prototype.executeQuery = function() {
   var deferred = $.Deferred();
   this.executeQueryAsync(
       function(){ deferred.resolve(arguments); },
       function(){ deferred.reject(arguments); }
   );
   return deferred.promise();
};

Wrapper with AngularJS's $q

SP.ClientContext.prototype.executeQuery = function() {
   var deferred = $q.defer();
   this.executeQueryAsync(
       function(){ deferred.resolve(arguments); },
       function(){ deferred.reject(arguments); }
   );
   return deferred.promise;
};

How do you use this?

var ctx = SP.ClientContext.get_current();
var web = ctx.get_web();
ctx.load(web);
var promise = ctx.executeQuery(); // look!  :-)

promise.done(function(){
  console.log(web.get_title());
});
promise.then(function(sArgs){
  //sArgs[0] == success callback sender
  //sArgs[1] == success callback args
}, function(fArgs){
  //fArgs[0] == fail callback sender
  //fArgs[1] == fail callback args.
  //in JSOM the callback args aren't used much - 
  //the only useful one is probably the get_message() 
  //on the fail callback
  var failmessage = fArgs[1].get_message();
});

This may seem to be just small syntactic sugar, but now you have JSOM returning a promise that you can chain, loop, combine and juggle to your heart's content!

Remember, jQuery.ajax, SPServices, AngularJS, and now JSOM all returns promise objects now.