Welcome to the Ultimate Guide on Deepmerge!

Deepmerge is a highly useful JavaScript library for deep merging objects. Whether you’re working with complex data structures or need to combine deeply nested objects, Deepmerge provides a powerful and flexible API for your needs.

Installation

  npm install deepmerge

Basic Usage

  const deepmerge = require('deepmerge');
  const object1 = {
    a: 1,
    b: 2,
    d: {
      e: 5
    }
  };
  const object2 = {
    b: 3,
    c: 4,
    d: {
      f: 6
    }
  };
  const result = deepmerge(object1, object2);
  console.log(result); 
  // Output: { a: 1, b: 3, c: 4, d: { e: 5, f: 6 } }

Handling Arrays

  const arrayMerger = (destinationArray, sourceArray, options) => sourceArray;
  const object1 = {
    array: [1, 2, 3]
  };
  const object2 = {
    array: [4, 5, 6]
  };
  const options = { arrayMerge: arrayMerger };
  const result = deepmerge(object1, object2, options);
  console.log(result);
  // Output: { array: [4, 5, 6] }

Custom Merging Function

  const mergeFunction = (target, source, optionsArgument) => {
    // Custom merging logic
    return source;
  };
  const result = deepmerge(object1, object2, { customMerge: mergeFunction });
  console.log(result);
  // Output depends on custom logic

App Example Using Deepmerge

Below is a simple example of a Node.js application that uses Deepmerge to combine configurations from different sources:

  const express = require('express');
  const deepmerge = require('deepmerge');

  const defaultConfig = {
    port: 3000,
    db: {
      host: 'localhost',
      user: 'root',
      password: 'password'
    }
  };

  const envConfig = {
    port: process.env.PORT || 3000,
    db: {
      password: process.env.DB_PASSWORD
    }
  };

  const finalConfig = deepmerge(defaultConfig, envConfig);

  const app = express();
  app.listen(finalConfig.port, () => {
    console.log(\`Server running on port \${finalConfig.port}\`);
  });

In this example, we’re merging environment-specific configurations with default configurations using Deepmerge.

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