How do you reliably determine whether an object is empty?

TL;DR

To reliably determine whether an object is empty, you can use Object.keys() to check if the object has any enumerable properties. If the length of the array returned by Object.keys() is zero, the object is empty.

const isEmpty = (obj) => Object.keys(obj).length === 0;

const obj = {};
console.log(isEmpty(obj)); // true

Using `Object.keys()`

The most common and reliable way to check if an object is empty is by using Object.keys(). This method returns an array of the object's own enumerable property names. If the length of this array is zero, the object is empty.

const isEmpty = (obj) => Object.keys(obj).length === 0;

const obj1 = {};
const obj2 = { key: 'value' };

console.log(isEmpty(obj1)); // true
console.log(isEmpty(obj2)); // false

Using `Object.entries()`

Another method is to use Object.entries(), which returns an array of the object's own enumerable property [key, value] pairs. If the length of this array is zero, the object is empty.

const isEmpty = (obj) => Object.entries(obj).length === 0;

const obj1 = {};
const obj2 = { key: 'value' };

console.log(isEmpty(obj1)); // true
console.log(isEmpty(obj2)); // false

Using `Object.values()`

Similarly, you can use Object.values(), which returns an array of the object's own enumerable property values. If the length of this array is zero, the object is empty.

const isEmpty = (obj) => Object.values(obj).length === 0;

const obj1 = {};
const obj2 = { key: 'value' };

console.log(isEmpty(obj1)); // true
console.log(isEmpty(obj2)); // false

Using a `for...in` loop

You can also use a for...in loop to check if an object has any properties. If the loop doesn't iterate over any properties, the object is empty.

const isEmpty = (obj) => {
  for (let key in obj) {
    if (obj.hasOwnProperty(key)) {
      return false;
    }
  }
  return true;
};

const obj1 = {};
const obj2 = { key: 'value' };

console.log(isEmpty(obj1)); // true
console.log(isEmpty(obj2)); // false

Edge cases

Prototype properties: The methods above only check for the object's own properties, not properties inherited from its prototype.
Non-enumerable properties: These methods do not account for non-enumerable properties.

How do you reliably determine whether an object is empty?

TL;DR