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

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.

You can also use Partial<T> type in method's signature but it this case you have to create an interface for your options:

interface IMyOptions {
  title: string;
  autoHideAfter: number;
}

And then the method's signature can look like:

error(message: string, options?: Partial<IMyOptions>);

Usage is the same as above.

Type Partial<T> should already be declared in global typings as following:

type Partial<T> = {
  [P in keyof T]?: T[P];
};

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.

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});

you can use optional variable by ? or if you have multiple optional variable by ..., example:

function details(name: string, country="CA", address?: string, ...hobbies: string) {
    // ...
}

In the above:

• name is required
• country is required and has a default value
• address is optional
• hobbies is an array of optional params