define function in typescriot code example

Example 1: typescript function

// Parameter type annotation
function greet(name: string): string {
 return name.toUpperCase();
}

console.log(greet("hello"));		// HELLO
console.log(greet(1));				// error, name is typed (string)

Example 2: types function typescript

interface Alternate_Syntax_4_Advanced {
    title: string;
    callback<T extends unknown[], R = unknown>(...args?: T): R;
}