type of a function in typescript 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: typescript function type

interface getUploadHandlerParams {
  checker : Function
}

Example 3: typescript default parameter

function sayName({ first, last = 'Smith' }: {first: string; last?: string }): void {
  const name = first + ' ' + last;
  console.log(name);
}

sayName({ first: 'Bob' });

Example 4: typescript annotate return type

function add(x: number, y: number): number {
  return x + y;
}