How to pass optional parameters while omitting some other optional parameters?

Question

Given the following signature:

export interface INotificationService {
    error(message: string, title?: string, autoHideAfter?: number);
}

How can I call the function error() not specifying the title parameter, but setting autoHideAfter to say 1000?

Answer 1

As specified in the documentation, use undefined:

export interface INotificationService {
    error(message: string, title?: string, autoHideAfter? : number);
}

class X {
    error(message: string, title?: string, autoHideAfter?: number) {
        console.log(message, title, autoHideAfter);
    }
}

new X().error("hi there", undefined, 1000);

Playground link.