What does exclamation point after variable mean in JavaScript? [duplicate]

I've seen in some React/TypeScript implementations such as :

ref={ ref => this.container = ref! }

What does the exclamation point means in ref!? Is that something specific in TypeScript, or a new standard JavaScript notation?


Solution 1:

In TypeScript, a postfix ! removes null and undefined from the type of an expression.

This is useful when you know, for reasons outside TypeScript's inference ability, that a variable that "could" be null or undefined actually isn't.