Introduction to deep-object-diff

The deep-object-diff library is an amazing tool for comparing JavaScript objects, allowing developers to identify changes with powerful precision. Whether you’re managing states in a frontend application or syncing data in a backend server, understanding the differences between objects is essential. In this article, we will explore various APIs provided by the deep-object-diff library along with practical examples, culminating in a complete application integration.

1. Basic Usage

The core functionality of deep-object-diff is its ability to compare JavaScript objects. Here’s a simple example:

  
    const { diff } = require('deep-object-diff');
    
    const obj1 = { name: 'John', age: 25 };
    const obj2 = { name: 'John', age: 30 };
    
    console.log(diff(obj1, obj2));
    // Output: { age: 30 }
  

2. Detailed Difference

In addition to basic differences, you might want to see what properties were added, removed, or changed:

  
    const { addedDiff, deletedDiff, updatedDiff } = require('deep-object-diff');
    
    const obj1 = { name: 'John', age: 25 };
    const obj2 = { name: 'Doe', age: 30, occupation: 'Engineer' };
    
    console.log(addedDiff(obj1, obj2));
    // Output: { occupation: 'Engineer' }
    
    console.log(deletedDiff(obj1, obj2));
    // Output: { name: 'John' }
    
    console.log(updatedDiff(obj1, obj2));
    // Output: { age: 30 }
  

3. Accumulating Changes

The diff method can be used to accumulate changes over time:

  
    const { diff } = require('deep-object-diff');
    
    let base = { a: 1, b: 2 };
    let changes = [{ b: 3, c: 4 }, { a: 2 }, { d: 5 }];
    
    let results = changes.reduce((acc, change) => {
      return Object.assign(acc, diff(acc, change));
    }, base);
    
    console.log(results);
    // Output: { a: 2, b: 3, c: 4, d: 5 }
  

4. Complete Application Example

Let’s integrate these APIs into a simple application. Imagine we are managing user profiles and need to track changes:

  
    const express = require('express');
    const { diff, addedDiff, deletedDiff, updatedDiff } = require('deep-object-diff');
    
    const app = express();
    app.use(express.json());
    
    let profiles = {
      john: { name: 'John Doe', age: 25, occupation: 'Developer' }
    };
    
    app.post('/updateProfile', (req, res) => {
      const { username, newProfile } = req.body;
      let existingProfile = profiles[username];
      
      if (existingProfile) {
        let differences = diff(existingProfile, newProfile);
        let added = addedDiff(existingProfile, newProfile);
        let deleted = deletedDiff(existingProfile, newProfile);
        let updated = updatedDiff(existingProfile, newProfile);
        
        profiles[username] = newProfile;

        res.json({
          message: 'Profile updated successfully',
          differences,
          added,
          deleted,
          updated
        });
      } else {
        profiles[username] = newProfile;
        res.json({ message: 'New profile created' });
      }
    });
    
    const PORT = process.env.PORT || 3000;
    app.listen(PORT, () => console.log(`Server running on port ${PORT}`));
  

In this example, we used deep-object-diff to track changes in user profiles and provide detailed feedback about what was added, deleted, or updated.

Understanding and managing object differences is crucial in modern applications, and deep-object-diff provides a powerful and easy-to-use toolkit for developers to achieve this.

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