Checking if an Object is Empty in JavaScript

In JavaScript, objects are used to store key-value pairs. Sometimes, you need to check if an object is empty or not. An empty object is one that has no keys or properties. In this tutorial, we will explore different ways to check if an object is empty in JavaScript.

Using a for…in loop

One way to check if an object is empty is by using a for...in loop. This method iterates over the object’s properties and returns false as soon as it finds one.

function isEmpty(obj) {
  for (var x in obj) { 
    return false; 
  }
  return true;
}

This method is simple and efficient, but it has a drawback: it does not check if the object’s properties are inherited from its prototype chain.

Using Object.keys()

Another way to check if an object is empty is by using Object.keys(), which returns an array of the object’s own enumerable property names.

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

This method is more concise and readable than the previous one, but it has a performance overhead due to the creation of an array.

Using Object.getOwnPropertyNames()

If you need to check if an object has any non-enumerable properties, you can use Object.getOwnPropertyNames().

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

This method is similar to the previous one but also includes non-enumerable properties.

Using jQuery

If you are using jQuery in your project, you can use its $.isEmptyObject() function.

if ($.isEmptyObject(obj)) {
  // do something
}

This method is convenient if you already have jQuery included in your project.

Performance Comparison

The performance of these methods may vary depending on the size of the object and the JavaScript engine. However, in general, the for...in loop is the fastest option for empty objects, while Object.keys() is slower due to the creation of an array.

To demonstrate this, let’s create a simple benchmark:

var obj = {};

function isEmpty1() {
  return Object.keys(obj).length === 0;
}

function isEmpty2() {
  for (x in obj) { 
    return false; 
  }
  return true;
}

console.time('isEmpty1');
for (i = 0; i < 100000; i++) {
  isEmpty1();
}
console.timeEnd('isEmpty1');

console.time('isEmpty2');
for (i = 0; i < 100000; i++) {
  isEmpty2();
}
console.timeEnd('isEmpty2');

This benchmark shows that the for...in loop is generally faster than Object.keys().

Conclusion

In conclusion, there are several ways to check if an object is empty in JavaScript. The choice of method depends on your specific needs and performance requirements. If you need a simple and efficient solution, the for...in loop may be the best option. However, if you prefer a more concise and readable solution, Object.keys() or $.isEmptyObject() may be a better choice.