How to Effectively Check for Empty JavaScript Objects?

Checking for Empty JavaScript Objects

When working with JavaScript, you may encounter scenarios where your application returns an empty object, denoted as { }. Determining the emptiness of an object is essential for proper data handling. This article explores several methods to test for empty JavaScript objects.

Method 1: for...in Loop and Object.hasOwn (ECMA 2022)

This method utilizes a for...in loop to iterate over an object's properties. If any own properties exist, it indicates that the object is not empty, returning false. Otherwise, it returns true.

function isEmpty(obj) {
  for (const prop in obj) {
    if (Object.hasOwn(obj, prop)) {
      return false;
    }
  }

  return true;
}

Method 2: Object.keys and length

While straightforward, this approach is less efficient as it creates an array of all property names, which has a complexity of O(N).

function isEmpty(obj) {
  return Object.keys(obj).length === 0;
}

Method 3: Type Checks for { }-like Objects

To differentiate between empty objects ({ }) and other objects with no own properties (e.g., Dates), type checks are necessary:

function isEmptyObject(value) {
  if (value == null) {
    return false; // null or undefined
  }

  if (typeof value !== 'object') {
    return false; // boolean, number, string, function, etc.
  }

  const proto = Object.getPrototypeOf(value);

  if (proto !== null && proto !== Object.prototype) {
    return false; // `Object.create(null)` or other objects with custom prototypes
  }

  return isEmpty(value); // check for any own properties
}

Method 4: Using Third-Party Libraries

Many popular JavaScript libraries provide functions for checking empty objects, such as:

• jQuery: jQuery.isEmptyObject
• lodash: _.isEmpty
• Underscore: _.isEmpty
• Hoek: Hoek.deepEqual
• ExtJS: Ext.Object.isEmpty
• AngularJS (version 1): angular.equals

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