When using destructuring, it's possible to create a pattern that has no effect. This happens when empty curly braces are used to the right of an embedded object destructuring pattern, such as:

// doesn't create any variables
const {a : {}} = foo;

In many cases, the empty object pattern is a mistake where the author intended to use a default value instead, such as:

// creates a variable a
const {a = {}} = foo;

Bad Practice

cosnt {} = foo;
const [] = foo;
const {a: {}} = foo;
const {a: []} = foo;
function foo({}) {}
function foo([]) {}
function foo({a: {}}) {}
function foo({a: []}) {}

Recommended

const {a = {}} = foo;
const {a = []} = foo;
function foo({a = {}}) {}
function foo({a = []}) {}