How to Compare Two Objects in JavaScript
In JavaScript, comparing two objects can sometimes be a bit tricky, especially when you want to ensure that they are not only equal in structure but also in the values of their properties. This article will guide you through various methods to compare two objects in JavaScript, including the use of strict equality, deep equality, and other techniques.
Firstly, it’s important to note that when using the strict equality operator (`===`), JavaScript compares both the structure and the values of the objects. However, this method only works if both objects are of the same type and have the same properties with identical values. If you want to compare two objects using strict equality, you can simply do the following:
“`javascript
const obj1 = { name: ‘John’, age: 30 };
const obj2 = { name: ‘John’, age: 30 };
console.log(obj1 === obj2); // Output: true
“`
As you can see, the objects `obj1` and `obj2` are strictly equal because they have the same structure and values.
However, if the objects have different structures or properties, the strict equality operator will return `false`. In such cases, you might want to use a deep equality comparison, which checks whether the objects have the same structure and values, even if the properties are in different orders or if some properties are missing.
One way to achieve deep equality is by using a recursive function that compares each property of the objects. Here’s an example:
“`javascript
function deepEqual(obj1, obj2) {
if (obj1 === obj2) {
return true;
}
if (typeof obj1 !== ‘object’ || obj1 === null || typeof obj2 !== ‘object’ || obj2 === null) {
return false;
}
const keys1 = Object.keys(obj1);
const keys2 = Object.keys(obj2);
if (keys1.length !== keys2.length) {
return false;
}
for (const key of keys1) {
if (!keys2.includes(key) || !deepEqual(obj1[key], obj2[key])) {
return false;
}
}
return true;
}
const obj1 = { name: ‘John’, age: 30, hobbies: [‘reading’, ‘swimming’] };
const obj2 = { name: ‘John’, age: 30, hobbies: [‘swimming’, ‘reading’] };
console.log(deepEqual(obj1, obj2)); // Output: true
“`
In this example, the `deepEqual` function recursively compares each property of the objects. If the objects have the same structure and values, the function returns `true`; otherwise, it returns `false`.
Another method to compare two objects is by using libraries such as Lodash, which provides a `isEqual` function that performs deep equality checks. Here’s an example:
“`javascript
const _ = require(‘lodash’);
const obj1 = { name: ‘John’, age: 30, hobbies: [‘reading’, ‘swimming’] };
const obj2 = { name: ‘John’, age: 30, hobbies: [‘swimming’, ‘reading’] };
console.log(_.isEqual(obj1, obj2)); // Output: true
“`
Using libraries like Lodash can simplify the process of comparing objects, but it’s important to note that they can add extra dependencies to your project.
In conclusion, comparing two objects in JavaScript can be done using strict equality, deep equality, or libraries like Lodash. Each method has its own advantages and disadvantages, so choose the one that best suits your needs.
