ECMAScript 6 arrow function that returns an object

ECMAScript 6 arrow function that returns an object

When returning an object from an arrow function, it seems that it is necessary to use an extra set of {} and a return keyword because of an ambiguity in the grammar.
That means I can’t write p => {foo: “bar”}, but have to write p => { return {foo: “bar”}; }.
If the arrow function returns anything other than an object, the {} and return are unnecessary, e.g.: p => “foo”.
p => {foo: “bar”} returns undefined.
A modified p => {“foo”: “bar”} throws “SyntaxError: unexpected token: ‘:’”.
Is there something obvious I am missing?


Solution 1:

You must wrap the returning object literal into parentheses. Otherwise curly braces will be considered to denote the function’s body. The following works:

p => ({ foo: 'bar' });

You don’t need to wrap any other expression into parentheses:

p => 10;
p => 'foo';
p => true;
p => [1,2,3];
p => null;
p => /^foo$/;

and so on.

Reference: MDN – Returning object literals

Solution 2:

You may wonder, why the syntax is valid (but not working as expected):

var func = p => { foo: "bar" }

It’s because of JavaScript’s label syntax:

So if you transpile the above code to ES5, it should look like:

var func = function (p) {
  "bar"; //obviously no return here!

Solution 3:

If the body of the arrow function is wrapped in curly braces, it is not implicitly returned. Wrap the object in parentheses. It would look something like this.

p => ({ foo: 'bar' })

By wrapping the body in parens, the function will return { foo: 'bar }.

Hopefully, that solves your problem. If not, I recently wrote an article about Arrow functions which covers it in more detail. I hope you find it useful. Javascript Arrow Functions