[Node Server Protection For Web Game?]

I am writing my own web game as I learn web programming.
For the next version I am moving most the code to a server.
This is the first time I am writing a server from scratch.

Using a Node server with Express and Sockets stacked in as the frame work.

What are tricks I can use to prevent malicious players from hacking the server?

Right now I am enclosing all incoming data in {} brackets and nothing gets ran without a 'typeof' verification that it is of the correct datatype.
No functions are being passed as data types so anything that returns as a typeof == 'function' gets scrapped.

Only after code that passes all my verifications and gets through proper processing returning the correct type of data gets transferred out of the {} fields.

 

[Introduce yourself]

My name is Tygari

Nationality: American
Sex: Female
Race: White
Height: 5"10'
Favorite band: ItaloBrothers
Favorite book: Imago
Favorite author: Octavia Butler
Favorite anime: Log Horizon
Known Languages: HTML, CSS, JavaScript, Node
Hobbies: Web Programming, Games, Cooking, Anime, Writing
Occupation: Failure