Simple JavaScript Map - Using an Object as the Return

Question

I'm studying the map function and tried to make a contrived example which I thought would work. This code works fine:

let students = [{name: 'Susan', grades: [88, 38, 28]}, {name: 'Robert', grades: [28,97, 17]}];
let newStudents = students.map((el) => el.name);  
console.log(newStudents); // [ 'Susan', 'Robert' ]

But what I really wanted was the following in the map function:

let newStudents = students.map((el) => {name: el.name});
// [ undefined, undefined ]
// I assumed to get back the following: [ {name: 'Susan'}, {name: 'Robert'} ]

Why is using an object in the return portion of the map function not allowed?

Try this let newStudents = students.map((el) => {return {name: el.name}}); — Timothy Lee
– Timothy Lee, Commented Jul 27, 2017 at 6:06

Tschallacka · Accepted Answer · 2017-07-27 06:49:44Z

4

You need to wrap the object in normal function parenthesis.

let newStudents = students.map((el) => ({name: el.name}));
                                        ^              ^

let students = [{name: 'Susan', grades: [88, 38, 28]}, {name: 'Robert', grades: [28,97, 17]}];
let newStudents = students.map((el) => ({name: el.name}));
console.log(newStudents);

edited Jul 27, 2017 at 6:49

answered Jul 27, 2017 at 6:05

Tschallacka

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2 Comments

qarthandso Over a year ago

Ah ok thank you. And why exactly do I need the extra parenthesis?

Kyle Richardson Over a year ago

It causes an explicit return. Without them or return the curly brakets denote a function block.

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