if the function takes no parameters, you are empty parenthesis.
const greet = () => "Hello";
console.log(greet()); If there's only on parameter, parentheses are optional.
const square = x => x * x;
console.log(square(4)); If there's only on parameter, parentheses are optional
const add = (a, b) => a + b;
console.log( add(2, 3) ); If the function body has more than one statement, you need to use curly braces and specify the return keyword (if you want to return something).
const greetPerson = name => {
const greeting = "Hello, " + name + "!";
return greeting;
}
console.log( greetPerson("Alice")); When directly returning and object literal, wrap the literal in parentheses to differentiate it from the function block.
const makePerson = (firstName, lastName) =>
({ first: firstName, last: lastName });
console.log( makePerson("John", "Doe") );
// Outputs: { first: 'John', last: 'Doe'}Arraow functions are particularly popular when used as short callbacks.
const numbers = [1,2,3,4];
const doubled = numbers.map(num => num * 2);
console.log(doubled);
//Outputs: [2,4,6,8]