How Can I Effectively Test for Empty JavaScript Objects?

Testing for Empty JavaScript Objects

When handling AJAX responses, it's common to encounter empty objects, such as var a = {};. Determining whether an object is empty is crucial for various application tasks.

Object.hasOwn() and for...in Loop:

For ECMAScript 2022 environments, the Object.hasOwn() method can be used in conjunction with a for...in loop to check for empty objects:

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

  return true;
}

This method iterates through all the object's own properties, and if any property is found, it indicates a non-empty object.

Distinguishing Empty Objects from Objects with No Own Properties:

If you need to differentiate between {}-like empty objects and objects with no own properties (e.g., Dates), additional type checks can be performed:

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

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

  const proto = Object.getPrototypeOf(value);
  if (proto !== null && proto !== Object.prototype) {
    return false; // consider 'Object.create(null)'
  }

  return isEmpty(value);
}

Alternative Methods:

If you don't have access to ES 2022 features, you can use the legacy Object.prototype.hasOwnProperty.call() method:

function isEmpty(obj) {
  for (var prop in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, prop)) {
      return false;
    }
  }

  return true;
}

Popular Library Functions:

Many popular libraries also provide functions to check for empty objects:

• jQuery: $.isEmptyObject({})
• lodash: _.isEmpty({})
• Underscore: _.isEmpty({})
• Hoek: Hoek.deepEqual({}, {})
• ExtJS: Ext.Object.isEmpty({})
• AngularJS (version 1): angular.equals({}, {})
• Ramda: R.isEmpty({})

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