Tutorials

Lodash _.merge() Object Method

Posted in lodash Tutorial

Updated on Apr 07, 2024

By Mari Selvan

👁️ 50 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of JavaScript development, managing complex objects and their properties efficiently is crucial. Lodash, a widely-used utility library, offers a plethora of functions to simplify object manipulation. Among these functions lies the _.merge() method, a powerful tool for merging two or more objects while handling nested properties with ease.

This method enhances code maintainability and readability, making it indispensable for developers dealing with complex data structures.

🧠 Understanding _.merge() Method

The _.merge() method in Lodash is designed to merge multiple objects into a single object, with nested properties recursively merged. This enables developers to combine and consolidate data from disparate sources effortlessly, simplifying data management and manipulation.

💡 Syntax

The syntax for the _.merge() method is straightforward:

syntax.js

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_.merge(object, [sources])

object: The destination object to merge into.
sources: The source objects to merge from.

📝 Example

Let's dive into a simple example to illustrate the usage of the _.merge() method:

example.js

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const _ = require('lodash');

const destinationObject = {
  name: 'John',
  age: 30,
  address: {
    city: 'New York',
    country: 'USA'
  }
};

const sourceObject = {
  age: 35,
  address: {
    city: 'San Francisco'
  }
};

const mergedObject = _.merge(destinationObject, sourceObject);

console.log(mergedObject);

In this example, destinationObject and sourceObject are merged using _.merge(), resulting in a new object containing the combined properties:

json

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{
  "name": "John",
  "age": 35,
  "address": {
    "city": "San Francisco",
    "country": "USA"
  }
}

🏆 Best Practices

When working with the _.merge() method, consider the following best practices:

Preserve Destination Object:

To prevent unintentional modification of the destination object, ensure that the destination object is a separate instance or clone.

example.js

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const destinationObject = {
  name: 'John',
  address: {
    city: 'New York'
  }
};

const sourceObject = {
  age: 30
};

const clonedDestination = _.cloneDeep(destinationObject);
const mergedObject = _.merge(clonedDestination, sourceObject);

console.log(mergedObject);

Handle Array Merging:

Be aware that _.merge() does not handle array merging by default. If you need to merge arrays within objects, consider using custom merging logic or Lodash's _.mergeWith() method.

example.js

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const destinationObject = {
  colors: ['red', 'green'],
};

const sourceObject = {
  colors: ['blue'],
};

const mergedObject = _.mergeWith(destinationObject, sourceObject, (objValue, srcValue) => {
  if(_.isArray(objValue)) {
    return objValue.concat(srcValue);
  }
});

console.log(mergedObject);
// Output: { colors: ['red', 'green', 'blue'] }

Avoid Circular References:

Exercise caution when dealing with objects containing circular references, as _.merge() does not handle circular references and may result in stack overflow errors.

📚 Use Cases

Configuration Merging:

_.merge() is particularly useful when merging configurations from multiple sources, such as default settings and user preferences, into a single configuration object.

example.js

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const defaultConfig = {
  theme: 'light',
  fontSize: 16
};

const userConfig = {
  theme: 'dark',
  showSidebar: true
};

const mergedConfig = _.merge(defaultConfig, userConfig);

console.log(mergedConfig);

Data Aggregation:

In data-intensive applications, _.merge() can be employed to aggregate data from various sources into a unified dataset, facilitating analysis and processing.

example.js

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const dataFromAPI = /* ...fetch data from API... */;
const localData = /* ...load data from local storage... */;

const aggregatedData = _.merge(dataFromAPI, localData);

console.log(aggregatedData);

Object Patching:

When updating an object with new information, _.merge() can be used to patch the existing object with the changes without losing existing data.

example.js

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const existingObject = /* ...retrieve existing object... */;
const changes = /* ...retrieve changes... */;

const patchedObject = _.merge(existingObject, changes);

console.log(patchedObject);

🎉 Conclusion

The _.merge() method in Lodash offers a versatile solution for merging objects and consolidating data from multiple sources effortlessly. Whether you're dealing with configuration settings, aggregating data, or updating objects dynamically, _.merge() provides a powerful tool for managing complex data structures in JavaScript.

By adhering to best practices and exploring diverse use cases, you can harness the full potential of the _.merge() method in your Lodash projects.