For example you have a TS app:

enum PaylerPosition {    Guard,    Forward,    Center}interface Player {    name: string;    position: PlayerPosition;}let kobe = {    name: 'Kobe',    position: PlayerPosition.Guard};

The problem for this piece of code is that, you can assign 'kobe' to null, or undefined. And compiler won't catch this error by defualt.

 

In TypeScritp 2, it includes a new rule:

"strictNullChecks": true

We can set this in tsconfig.json file.

Then it will catch if variable are assigned to 'null' or 'undefined'.