You can use a for…in loop with an Object.hasOwn (ECMA 2022+) test to check whether an object has any own properties:

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

  return true;
}

If you also need to distinguish {}-like empty objects from other objects with no own properties (e.g. Dates), you can do various (and unfortunately need-specific) type checks:

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

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

  const proto = Object.getPrototypeOf(value);

  // consider `Object.create(null)`, commonly used as a safe map
  // before `Map` support, an empty object as well as `{}`
  if (proto !== null && proto !== Object.prototype) {
    return false;
  }

  return isEmpty(value);
}

Note that comparing against Object.prototype like in this example will fail to recognize cross-realm objects.

Do not use Object.keys(obj).length. It is O(N) complexity because it creates an array containing all the property names only to get the length of that array. Iterating over the object accomplishes the same goal but is O(1).

For compatibility with JavaScript engines that don’t support ES 2022+, const can be replaced with var and Object.hasOwn with Object.prototype.hasOwnProperty.call:

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

  return true
}

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

jQuery:

CopyjQuery.isEmptyObject({}); // true

lodash:

Copy_.isEmpty({}); // true

Underscore:

Copy_.isEmpty({}); // true

Hoek:

CopyHoek.deepEqual({}, {}); // true

ExtJS:

CopyExt.Object.isEmpty({}); // true

AngularJS (version 1):

Copyangular.equals({}, {}); // true

Ramda:

CopyR.isEmpty({}); // true

Below code(jQuery.isEmptyObject(anyObject) function is already provided) works perfectly fine, no need to write one of your own.

   // works for any Object Including JSON(key value pair) or Array.
  //  var arr = [];
  //  var jsonObj = {};
    if (jQuery.isEmptyObject(anyObjectIncludingJSON))
    {
       console.log("Empty Object");
    }

Try below code snippet:-

if(!Object.keys(response.data).length){
     console.log("no data found");
 }

If you are getting data as empty object like data: {}, then you should check if there is any key inside the object or not.

You were testing sellers which is not empty because it contains mergedSellerArray. You need to test sellers.mergedSellerArray

let sellers = {
  "mergedSellerArray": {}
};
if (Object.keys(sellers.mergedSellerArray).length === 0 && sellers.mergedSellerArray.constructor === Object) {
  console.log("sellers is empty!");
} else {
  console.log("sellers is not empty !");
}

Use length to check if the object is empty or not.

var isEmpty = (response || []).length === 0;

you can check if it has any keys:

Object.keys(dataJson).length

Use $.isArray() to check whether an object is an array. Then you can check the truthness of the length property to see whether it is empty.

if( !$.isArray(siteArray) ||  !siteArray.length ) {
    //handler either not an array or empty array
}

function isArrayEmpty(array) {
    return array.filter(function(el) {
        return !jQuery.isEmptyObject(el);
    }).length === 0;
}

jsFiddle Demo

Passes all of your tests.

A pure JavaScript solution would be to replace !jQuery.isEmptyObject(el) with Object.keys(el).length !== 0

Edit: Using Array.prototype.every

function isArrayEmpty(array) {
    return array.every(function(el) {
        return jQuery.isEmptyObject(el);
    });
}

i don't know what is you meaning about empty object, but if you consider

{}

as a empty object, i suppose you use the code below

var obj = {};

if (Object.keys(obj).length === 0) {
    alert('empty obj')
}