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Merge 2 Objects Javascript: Javascript Explained

Table of Contents

Merging objects with JavaScript is an incredibly useful process which can often help make coding faster and more accessible. In this article, we’ll explore the process of merging objects in JavaScript, discuss its syntax and benefits, and explore some common challenges that come up when merging objects with JavaScript. We’ll also discuss some of the more popular use cases for the process. By the end, you should have a clear understanding of how to merge two objects in JavaScript.

Introduction to Merging Objects with Javascript

Merging is an essential part of many programming operations. Merging refers to the merging of two or more elements into one entity. In contemporary web development, much of the merging process involves either merging two objects into one object, or merging two arrays into one array.

Merging objects utilizes the syntactical components of the JavaScript language in order to create a larger object from two smaller ones. The basic syntax looks like the following:

const newObject = { ... objectOne, ... objectTwo };

The ellipses (…) indicate that both of the objects being merged into the new object are flattened into one. This process is known as shallow merging and will be discussed further in the next section.

The Syntax for Merging Objects

Merely looking at the syntax for merging objects can make it a bit confusing, as the structure of the code alone isn’t immediately explanatory. To fully understand what’s happening when merging objects, it helps to break it down. Essentially, when performing shallow merging, you are creating a new, larger object with values from both original objects.

The ellipses (…) spread the contents of both merging objects into the new one. The syntax is basically shorthand for writing out each individual element in both objects. For example, let’s assume we have two objects, objectOne and objectTwo. If we wanted to merge these two objects manually, the syntax would look like this:

let objectOne = { keyOne: ‘valueOne, keyTwo: ‘valueTwo’ }; let objectTwo = { keyThree: ‘valueThree, keyFour: ‘valueFour’ }; let newObject = { keyOne: ‘valueOne, keyTwo: ‘valueTwo’, keyThree: ‘valueThree, keyFour: ‘valueFour’ }; 

When using the shallow merging syntax, they all become much simpler:

let objectOne = { keyOne: ‘valueOne, keyTwo: ‘valueTwo’ }; let objectTwo = { keyThree: ‘valueThree, keyFour: ‘valueFour’ };let newObject = { ...objectOne, ...objectTwo };

Merging Primitive Types

When discussing merging, it is helpful to understand types of data as well as structures. Primitive data types are values that are not objects or arrays and are numbers, strings, booleans, symbols and (in some cases) null and undefined. When merging primitive data types, it is important to note that only one of each type will be merged into the new set.

For example, say we have an array of primitive types like this: let arrOne = [1, ‘foo’]; and we have another array in this classic style let arrTwo = [2, ‘bar’]. Merging these together would look like this: let arrMerged = […arrOne, …arrTwo]. The new array would look like this [1, ‘foo’, 2, ‘bar’], with any duplicate values either dropped (in case of numbers) or overwritten (in case of strings).

Merging Arrays and Objects Together

Merging arrays and objects together is a bit more complex than merging primitive types. Objects tend to contain more complex values than arrays. As such, a simple shallow merge may not get the job done for more complex objects.

Imagine that you have two objects that represent a blog post and its comments respectively. Then you have a third array that contains information about tags that have been assigned to the blog post. With a shallow merge, these three sets will all exist as individual entities in the new object. To get these elements to live within the same object, you will need to specify each element within the new object like so:

let blogPost = { title: 'My Blog Post', content: 'This is a blog post' }; let comments = { comments: ['Comment 1', 'Comment 2'] }; let tags = [ 'tag1', 'tag2' ]; let mergedPost = {     ...blogPost,     ...comments,     tags: [...tags] };

Merging Complex Objects

Merging complex objects should not be done superficially with shallow merging. Merging complex objects runs the risk of accidentally overwriting vital pieces of data from one or more of the merging objects. For example, if two of the merging objects contained an identical key (e.g. ‘title’), only one value would persist in the merged object.

In order to ensure that all desired information is kept within the merged object, it is necessary to manually write out each object. It may look something like this:

let objOne = { title: 'My Title', content: 'My Content', tags: ['tag1', 'tag2'] }; let objTwo = { title: 'My Other Title', comments: ['Comment 1', 'Comment 2'] }; let mergedObj = {     title: objOne.title + objTwo.title,     content: objOne.content + objTwo.content,     tags: [...objOne.tags],     comments: [...objTwo.comments] };

Benefits of Object Merging

Object merging can be beneficial in many ways. Primarily, it can help save time and allow for easier re-use of code suites in large projects. By combining individual components into a single object instead of hard-coding each separate component into hard-coded parameters within a function call, there is less clutter within functions and thus the code can be easier to read and maintain.

Merging two large programs into a single entity also reduces the number of lines of code that need to be written. This makes debugging easier because in many instances fewer lines of code mean fewer breaks in the logic.

Common Challenges When Merging Objects

As powerful as it can be, there are some pitfalls to consider when merging objects. Chief among these is that you must ensure that all desired information is included in the new object without accidentally overwriting anything important. This hurdle can be easily surmounted with careful consideration while coding.

Perhaps even more pressing are potential issues arising from TypeScript implementations in which using elliptical code syntax while merging objects may cause unexpected results. TypeScript requires developers to pass types along with values and using flagrant domineering merges across large datasets could cause unexpected changes to types or data inconsistencies due to type mismatches.

Use Cases for Object Merging in Javascript

Object merging is an invaluable tool for developers of all levels. It can help streamline development for large applications by easily providing access to entire sets of information from one source of code. It can also aid new developers immensely by helping them understand how data flows from multiple sources.

Object merges can also be used in situations that involve passing large chunks of data over APIs or websockets for example. By combining entire JSON string sets into one statement instead of multiple separate calls, web developers can reduce the total amount of time needed from making multiple calls to sent one message.

Conclusion

In conclusion, object merging is an incredibly powerful tool that is integral to many web development operations today. Despite its impressive power however, it is a tool that should be used with caution as it can easily cause unexpected consequences if not used properly.

To ensure success when merging objects together in JavaScript, developers should try to think through their process both before writing it out as code and while they’re actually writing it. Additionally, those using TypeScript should pay extra attention to how their scripts are using data types across multiple systems in order to avoid any inconsistencies.

Nisha Kumari

Nisha Kumari

Nisha Kumari, a Founding Engineer at Bito, brings a comprehensive background in software engineering, specializing in Java/J2EE, PHP, HTML, CSS, JavaScript, and web development. Her career highlights include significant roles at Accenture, where she led end-to-end project deliveries and application maintenance, and at PubMatic, where she honed her skills in online advertising and optimization. Nisha's expertise spans across SAP HANA development, project management, and technical specification, making her a versatile and skilled contributor to the tech industry.

Written by developers for developers

This article was handcrafted with by the Bito team.

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