typescript type for function parameter function code example

Example 1: typescript default parameter

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

sayHello(); // Prints 'hello'

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

Example 2: types function typescript

interface Better_still_safe_but_way_more_flexible_fix {
    title: string;
    callback: <T = unknown, R = unknown>(args?: T) => R;
}
interface Alternate_Syntax_4_Better_still_safe_but_way_more_flexible_fix {
    title: string;
    callback<T = unknown, R = unknown>(args?: T): R;
}