What does the exclamation mark do in TypeScript

Question

When looking at the sourcecode for a tslint rule, I came across the following statement:

if (node.parent!.kind === ts.SyntaxKind.ObjectLiteralExpression) {
    return;
}

Notice the ! operator after node.parent?

What is it and how does it work?

Answer 1

The exclamation mark is called the non-null assertion operator. The type checker sometimes does not work so you can include this explicitly.