Are facebook games are made by flash or HTML5. Example: Candy crush saga.
Facebook games can be done in both or even using 3D engines like Unity. You can definitely develop games running in Facebook by using Construct 2 if this is your question.
Develop games in your browser. Powerful, performant & highly capable.
Lots of modern 2D games are made with unity and not with flash anymore.
With Construct 2 can make games for facebook and type Candy crush saga but with limitations.