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

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?

Solution 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.

Solution 2:

Unfortunately there is nothing like this in TypeScript (more details here: https://github.com/Microsoft/TypeScript/issues/467)

But to get around this you can change your params to be an interface:

export interface IErrorParams {
  message: string;
  title?: string;
  autoHideAfter?: number;
}

export interface INotificationService {
  error(params: IErrorParams);
}

//then to call it:
error({message: 'msg', autoHideAfter: 42});

Solution 3:

Another approach is:

error(message: string, options?: {title?: string, autoHideAfter?: number});

So when you want to omit the title parameter, just send the data like that:

error('the message', { autoHideAfter: 1 })

I'd rather this options because allows me to add more parameter without having to send the others.