If you spend enough time working with JavaScript, you'll eventually hit a wall trying to compare two objects. Maybe you're checking if user data has changed, validating form inputs, or testing your code. You reach for the === operator and... nothing works the way you expected.
That's when most developers discover they need a better solution. Two popular approaches emerge: lodash isEqual and JSON.stringify. But which one should you actually use? Let's break down these methods in plain English so you can make the right choice for your project.
What's the Problem with Comparing Objects in JavaScript?
Before we dive into solutions, lets understand the problem. In JavaScript, objects are reference types. When you compare two objects with ===, you're not comparing their contents. You're checking if they point to the exact same spot in memory.
Here's what that means in practice:
const obj1 = { name: 'John', age: 30 };
const obj2 = { name: 'John', age: 30 };
console.log(obj1 === obj2); // false
Even though these objects look identical, JavaScript says they're different. This is where lodash isequal vs json stringify comes into play. Both methods try to solve this problem, but they take very different approaches.
Understanding JSON Stringify for Object Comparison
The JSON.stringify method converts JavaScript objects into JSON strings. Once you have strings instead of objects, you can compare them with the simple === operator.
Here's the basic approach:
const obj1 = { name: 'John', age: 30 };
const obj2 = { name: 'John', age: 30 };
console.log(JSON.stringify(obj1) === JSON.stringify(obj2)); // true
It seems simple, right? Convert both objects to strings and compare. This works in many basic cases, and you don't need any external libraries.
The Big Problems with JSON Stringify
But JSON stringify has some serious limitations. First, the order of properties matters. If two objects have the same data but different property order, JSON stringify will say they're different:
const obj1 = { name: 'John', age: 30 };
const obj2 = { age: 30, name: 'John' };
console.log(JSON.stringify(obj1) === JSON.stringify(obj2)); // false
Second, JSON stringify cant handle certain JavaScript types. Functions, undefined values, Symbols, and dates don't serialize properly. You'll lose data or get unexpected results.
According to big write hook, understanding these limitations is crucial before choosing your comparison method.
What is Lodash isEqual?
Lodash is a popular JavaScript utility library that provides helpful functions for common programming tasks. The isEqual function is specifically designed for deep equality checks between two values.
Unlike JSON stringify, lodash isequal was built from the ground up to handle object comparison correctly. It checks the actual content of objects, arrays, dates, and other types without converting them to strings first.
Basic usage looks like this:
const _ = require('lodash');
const obj1 = { name: 'John', age: 30 };
const obj2 = { age: 30, name: 'John' };
console.log(_.isEqual(obj1, obj2)); // true
Notice how property order doesn't matter anymore. Lodash isEqual focuses on whether the actual values match, not their position.
Deep Dive: How Lodash isEqual Works
Lodash isEqual performs a recursive deep comparison. It walks through every property and nested property of both objects, comparing values along the way.
The function handles many data types correctly:
- Objects and arrays - Compares all nested properties
- Dates - Compares the actual timestamps
- Regular expressions - Checks the pattern and flags
- Functions - Compares by reference
- Special values - Handles NaN, null, undefined properly
This makes lodash isequal much more reliable for real-world applications where data can get complex.
Performance Comparison: Speed and Efficiency
When we talk about lodash isequal vs json stringify, performance is a key consideration. Which one is faster?
For simple, flat objects, JSON stringify is usually faster. Converting to strings and comparing is a straightforward operation that JavaScript engines optimize well.
However, for nested or complex objects, lodash isEqual often performs better. Why? Because JSON stringify has to convert the entire object tree to a string first. With deeply nested structures, this creates a lot of overhead.
Here's what affects performance:
- Object size - Larger objects favor lodash isEqual
- Nesting depth - Deep nesting hurts JSON stringify more
- Property count - More properties slow down both methods
- Data types - Special types slow down JSON stringify significantly
Feature Comparison Table
| Feature | Lodash isEqual | JSON Stringify |
| Property order | Doesn't matter | Matters significantly |
| Nested objects | Handles perfectly | Works but slower |
| Arrays | Deep comparison | String comparison |
| Dates | Compares correctly | Converts to strings |
| Functions | Reference comparison | Ignored completely |
| Undefined values | Preserved | Removed from output |
| NaN values | Handles correctly | Converts to null |
| Circular references | Can detect | Throws errors |
| Library needed | Yes (lodash) | No (built-in) |
| Bundle size impact | ~24KB (lodash) | 0 bytes |
| Edge case handling | Excellent | Poor |
When to Use JSON Stringify
Despite its limitations, JSON stringify has legitimate use cases. You should consider it when:
You need a quick solution without dependencies. If you're working on a small project or prototype, adding lodash might feel like overkill.
You're comparing simple, flat objects. When your objects don't have nested structures, functions, or special types, JSON stringify works fine.
Property order is consistent. If you control how objects are created and can guarantee property order, this method is safe.
Performance is critical for simple cases. For small objects in performance-sensitive code, the native JSON stringify can be faster.
When to Use Lodash isEqual
Lodash isEqual is the better choice for most professional applications. Use it when:
You need reliable comparisons. Production code shouldn't break because of property order or data types.
You're working with complex data structures. Nested objects, arrays within objects, mixed types - lodash handles them all.
You cant control input format. When data comes from APIs, user input, or third-party sources, you need robust comparison.
You value maintainability. Future developers (including yourself) will understand _.isEqual(a, b) more easily than worrying about JSON stringify quirks.
The Bundle Size Question
One common arguement against lodash isEqual is bundle size. Adding lodash to your project increases your JavaScript bundle, which can affect page load times.
The full lodash library is about 24KB minified and gzipped. However, you don't need the entire library. You can import just the isEqual function:
import isEqual from 'lodash/isEqual';
This significantly reduces the bundle size impact. Modern bundlers like webpack will tree-shake unused code, so you only ship what you actually use.
Handling Edge Cases
Let's look at some tricky scenarios where lodash isequal vs json stringify really matters.
Comparing Arrays
Both methods can compare arrays, but with different results:
const arr1 = [1, 2, { nested: true }];
const arr2 = [1, 2, { nested: true }];
// JSON stringify
JSON.stringify(arr1) === JSON.stringify(arr2); // true
// Lodash
_.isEqual(arr1, arr2); // true
For this simple case, both work. But watch what happens with undefined:
const arr1 = [1, undefined, 3]; const arr2 = [1, null, 3]; JSON.stringify(arr1); // "[1,null,3]" JSON.stringify(arr2); // "[1,null,3]" _.isEqual(arr1, arr2); // false
Lodash correctly identifies these as different, while JSON stringify loses the distinction.
Working with Dates
Dates are another problematic area:
const date1 = new Date('2024-01-01');
const date2 = new Date('2024-01-01');
// JSON stringify converts to strings
JSON.stringify(date1) === JSON.stringify(date2); // true
// But this is fragile
const obj1 = { created: new Date('2024-01-01') };
const obj2 = { created: new Date('2024-01-01') };
JSON.stringify(obj1) === JSON.stringify(obj2); // true
_.isEqual(obj1, obj2); // true
Both work here, but lodash isEqual understands that dates are timestamps and compares them semantically.
Practical Examples from Real Projects
Let's look at how developers use lodash isequal vs json stringify in actual applications.
Form Validation
When building forms, you often need to check if data has changed:
// Initial form data
const originalData = {
username: 'john_doe',
email: 'john@example.com',
preferences: {
notifications: true,
theme: 'dark'
}
};
// Current form data
const currentData = getUserFormData();
// Check if user made changes
if (!_.isEqual(originalData, currentData)) {
showSaveButton();
}
Using JSON stringify here would be risky because you can't control how the form library structures the data object.
Caching API Responses
Many apps cache API responses to avoid redundant network requests:
const cache = new Map();
function fetchUser(userId) {
const cacheKey = userId;
if (cache.has(cacheKey)) {
return cache.get(cacheKey);
}
// Fetch from API
const userData = api.getUser(userId);
cache.set(cacheKey, userData);
return userData;
}
In this scenerio, using lodash isEqual to compare cached data with new responses helps you determine if you need to update the UI.
Common Mistakes to Avoid
When working with object comparison, developers often make these mistakes:
Assuming JSON stringify always works. Don't use it blindly without understanding the limitations.
Not testing edge cases. Always test with dates, undefined values, and nested structures.
Ignoring performance implications. Profile your code if you're comparing objects frequently in loops.
Using the wrong tool for the job. Simple cases might not need lodash, complex cases definitely do.
Which One is Better?
So in the battle of lodash isequal vs json stringify, which one wins?
For most professional applications, lodash isEqual is the better choice. It's more reliable, handles edge cases correctly, and doesn't break when data structures change slightly.
JSON stringify is acceptable for:
- Quick prototypes
- Simple, flat objects
- Situations where you absolutely can't add dependencies
But if you're building software that other people will use and maintain, invest in the proper tool. The small bundle size cost of lodash isEqual pays for itself in prevented bugs and maintainence time saved.
Key Takeaways
- JavaScript's === operator doesn't work for comparing object contents
- JSON stringify is fast for simple objects but has many limitations
- Property order affects JSON stringify but not lodash isEqual
- Lodash isEqual handles dates, functions, and special values correctly
- Bundle size concerns can be mitigated by importing only what you need
- For production code, lodash isEqual is usually the safer choice
- JSON stringify works fine for prototypes and simple use cases
Final Verdict
The choice between lodash isequal vs json stringify ultimately depends on your specific needs. However, the trend in modern JavaScript development strongly favors robust, tested solutions like lodash isEqual.
Yes, it requires adding a dependency. Yes, it increases your bundle size slightly. But it also prevents bugs, handles edge cases gracefully, and makes your code more maintainable. These benefits far outweigh the costs in most professional environments.
If you're just learning or building something small, feel free to experiment with JSON stringify. You'll quickly discover its limitations, and then you'll understand why lodash isEqual exists.
For serious applications, save yourself the headache and use lodash isEqual from the start. Your future self will thank you.
Frequently Asked Questions
Q: Can I use JSON stringify to compare objects with functions? No, JSON stringify removes functions from objects entirely. If your objects contain functions, they won't be compared at all.
Q: Is lodash isEqual slower than JSON stringify? For simple objects, JSON stringify is faster. For complex nested structures, lodash isEqual often performs better because it doesn't need to serialize everything to strings first.
Q: Do I need the entire lodash library to use isEqual? No, you can import just the isEqual function to minimize bundle size impact. Use import isEqual from 'lodash/isEqual' instead of importing all of lodash.
Q: Will JSON stringify work for comparing arrays? It works for simple arrays, but fails with arrays containing undefined values or objects where property order might vary.
Q: Can lodash isEqual handle circular references? Lodash isEqual can detect circular references, while JSON stringify will throw an error when it encounters them.
Q: Which method should I use for React component props comparison? React's internal comparison uses a shallow check. For deep comparisons in shouldComponentUpdate or React.memo, lodash isEqual is the recommended approach.