Function definition when to use ( ) and when not to use them?

JavaScript
1

wrt chapter https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/es6/write-concise-object-literal-declarations-using-simple-fields and coming from Java background, it is super confusing with flexible ways of defining function in JS

Way 1

const getMousePosition = (x, y) => ({ x, y });

Note parenthesis against the function body

Way 2

const createPerson = (name, age, gender) => {
  "use strict";
  // change code below this line
  return {
    name,
     age,
     gender
  };
  // change code above this line
};
console.log(createPerson("Zodiac Hasbro", 56, "male")); // returns a proper object

No parenthesis in this case.

  • Please clarify when to use ( ) and when not to use it ?
  • Can I use ( ) in 2nd case ?

Thanks,
Vikram

2

MDN is your friend any time you have doubt of this sort.

If you look at the documentation for arrow function you’ll see under the advanced syntax the following example:

// Parenthesize the body of function to return an object literal expression:
params => ({foo: bar})

or in other word, if you use pares around, means you want to return an Object.

So this are equivalent:

() => {
 const obj = { a:1, b:2 };
 return obj;
}

// equivalent to
() => ({ a:1, b: 2 })

Hope this helps :+1:

2 Likes
4

Thanks for quick clarifications.

Regards,
Vikram