It is destructuring assignment.
The destructuring assignment syntax is a JavaScript expression that
makes it possible to unpack values from arrays, or properties from
objects, into distinct variables.
Example (ES6):
var person = {firstname: 'john', lastname: 'doe'};
const firstname = person.firstname;
const lastname = person.lastname;
// same as this
const { firstname, lastname } = person;
You can find more info at MDN
EDIT: also for developers familiar with Python language it can be interesting to compare with Python unpacking syntax.
Python2.7:
>>> _tuple = (1, 2, 3)
>>> a, b, c = _tuple
>>> print(a, b, c)
(1, 2, 3)
With new feature of Python3, like PEP 3132 you can also do following:
>>> _range = range(5)
>>> a, *b, c = _range
>>> print(a, b, c)
0 [1, 2, 3] 4
Examples are added, because knowing already similar approach from other languages you can grasp JS idea more quicker.