how to give optional arguments in typescript code example

Example 1: typescript optional parameters

// Optional Parameters
sayHello(hello?: string) {
	console.log(hello);
}

sayHello(); // Prints 'undefined'

sayHello('world'); // Prints 'world'

Example 2: typescript optional parameters

// Default Parameters
sayHello(hello: string = 'hello') {
  console.log(hello);
}

sayHello(); // Prints 'hello'

sayHello('world'); // Prints 'world'

Example 3: How to pass optional parameters while omitting some other optional parameters?

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);