Is it possible to define a dynamically named property using object literal in JavaScript?

Question

Consider the following

var a = {foo: \"bar\"};

Equivalent to

var a = {};
a.foo = \"bar\";

Equivalent to

Answer 1

ES6 supports computed properties.

// code from my original question now works in ES6 !
let b = "foo";
let a = { [b]: "bar" };

a.foo; //=> "bar"

Any expression can be used within the [] to define the property name

let a = {
  [(xs => xs.join(''))(['f','o','o'])]: 'bar'
};

a.foo; //=> "bar"

If you need to rely on this behavior in an ES5 world, you can lean on the very capable babel.js to transpile your ES6 code to ES5-compatible code.