JavaScript Arrow Functions

Basic - No parameter then requires Parentheses

const hello = () => "hello";
//USAGE:
console.log(hello());//Result: "hello"

Basic with parameter - No Parentheses required

hello = name => "Hello " + name;
//USAGE:
console.log(hello('John')); //Result: "Hello John"

Parentheses required if:

  1. 2 or more parameters
  2. Rest parameters
  3. Destructuring
  4. Objects

Examples

1. 2 or more parameters

hello = (fname,lname) => "hello" + fname + " " + lname;

2. Rest parameters

const numbers = (first, ...rest) => rest;
console.log(nums(1, 2, 3, 4));  //Result: [ 2, 3, 4 ]

3. Destructuring

const stateCapital = {
    state: "California",
    capital: "Sacramento"
 };
 const travel = ({capital}) => capital;
 console.log(travel(stateCapital)); //Result: "Sacramento"

4. Objects

const f = () => ({
    city:"Sacramento"
   })
   console.log(f().city)//Result: "Sacramento"

Object: ERROR if no Parentheses

const f = () => {
    city: "Sacramento"
}