javascript/1-js/05-data-types/05-array-methods/7-map-objects

let john = { name: "John", surname: "Smith", id: 1 };
let pete = { name: "Pete", surname: "Hunt", id: 2 };
let mary = { name: "Mary", surname: "Key", id: 3 };

let users = [ john, pete, mary ];


let usersMapped = users.map(user => ({
  fullName: `${user.name} ${user.surname}`,
  id: user.id
}));

/*
usersMapped = [
  { fullName: "John Smith", id: 1 },
  { fullName: "Pete Hunt", id: 2 },
  { fullName: "Mary Key", id: 3 }
]
*/

alert( usersMapped[0].id ); // 1
alert( usersMapped[0].fullName ); // John Smith

Please note that in the arrow functions we need to use additional brackets.

We can't write like this:

let usersMapped = users.map(user => {
  fullName: `${user.name} ${user.surname}`,
  id: user.id
});

As we remember, there are two arrow functions: without body value => expr and with body value => {...}.

Here JavaScript would treat { as the start of function body, not the start of the object. The workaround is to wrap them in the "normal" brackets:

let usersMapped = users.map(user => ({
  fullName: `${user.name} ${user.surname}`,
  id: user.id
}));

Now fine.

solution.md