How to Determine Equality for Two Javascript Objects?

How to determine equality for two JavaScript objects?

When working with JavaScript, you may come across situations where you need to compare two objects to check if they are equal. However, JavaScript does not provide a built-in method to directly compare objects for equality. In this blog post, we will explore different approaches to determine equality for two JavaScript objects.

Approach 1: JSON.stringify

One way to compare objects is by converting them to JSON strings using the JSON.stringify() method and then comparing the resulting strings. This approach works well for simple objects without circular references.

Here’s an example:

const obj1 = { name: 'John', age: 25 };
const obj2 = { age: 25, name: 'John' };

const isEqual = JSON.stringify(obj1) === JSON.stringify(obj2);
console.log(isEqual); // true

This approach converts both objects to strings and compares them. However, it has limitations when dealing with complex objects that contain functions, undefined values, or circular references.

Approach 2: Deep Equality Check

If you need to compare complex objects or handle circular references, you can use a deep equality check. This approach recursively compares each property of the objects to determine if they are equal.

Here’s an example:

function deepEqual(obj1, obj2) {
  if (obj1 === obj2) {
    return true;
  }

  if (typeof obj1 !== 'object' || typeof obj2 !== 'object' || obj1 === null || obj2 === null) {
    return false;
  }

  const keys1 = Object.keys(obj1);
  const keys2 = Object.keys(obj2);

  if (keys1.length !== keys2.length) {
    return false;
  }

  for (let key of keys1) {
    if (!keys2.includes(key) || !deepEqual(obj1[key], obj2[key])) {
      return false;
    }
  }

  return true;
}

const obj1 = { name: 'John', age: 25 };
const obj2 = { age: 25, name: 'John' };

const isEqual = deepEqual(obj1, obj2);
console.log(isEqual); // true

This approach recursively compares each property of the objects using a custom deepEqual() function. It handles nested objects and circular references by traversing the properties and comparing them.

Approach 3: Lodash isEqual

If you prefer using a library, Lodash provides a convenient method called isEqual() to compare objects for equality.

Here’s an example:

const _ = require('lodash');

const obj1 = { name: 'John', age: 25 };
const obj2 = { age: 25, name: 'John' };

const isEqual = _.isEqual(obj1, obj2);
console.log(isEqual); // true

Lodash’s isEqual() method performs a deep comparison of the objects and returns true if they are equal.

These are three different approaches to determine equality for two JavaScript objects. Choose the one that best suits your requirements and the complexity of your objects.

Remember to consider the limitations and performance implications of each approach when comparing objects.

How to Determine Equality for Two Javascript Objects?