adding types to parameters typescript code example

Example 1: how to make a parameter optional in typescript

// Optional parameter
function foo(x?: number) {
    console.log("x : "+ x);
}
foo();
foo(6);

Example 2: typescript function as parameter

function createPerson(name: string, doAction: () => void): void {
  console.log(`Hi, my name is ${name}.`);
  doAction(); // doAction as a function parameter.
}

// Hi, my name is Bob.
// performs doAction which is waveHands function.
createPerson('Bob', waveHands());