How Does ReactJS’s Bundle Splitting Work?

The technique of code splitting is employed to segment extensive files into smaller and more manageable components. It enables the code to be downloaded either as a complete entity, or to be requested and retrieved instantly. Although not a new concept, comprehending it may prove to be a challenge.

Segmenting code into distinct bundles preserves the HTML, CSS, and JavaScript files as negligible as possible. A decrease in website performance may occur if any application size is enlarged.

Although JavaScript is renowned for its simple programming, the development of intricate applications and frameworks can rapidly become intricate. Numerous dependencies must be considered, resulting in even the simplest of JavaScript programs containing a significant amount of code.

The greater the number of lines of code, the more sluggish the loading time of webpages in browsers. Thus, the amount of JavaScript dependencies required for the application should be determined based on its speed requirements. To strike a balance between the two factors, code-splitting in React can be utilized.

What does code splitting refer to in React.js?

Code-splitting is an attribute supported by numerous web bundlers including webpack, rollup, and browserify. This technique enables the dynamic loading of various bundles, making it particularly valuable for websites featuring a sizeable number of components by reducing the overall size of the website. By employing code-splitting, web developers ensure that their sites remain effective and lightweight.

Integrating external libraries into webpack bundles causes an increase in its overall size and weight. This approach aids in the creation of executable and runnable bundles. In addition, webpack bundle splitting optimizes the code by encompassing all essential imports and files.

React’s code splitting feature enables the identification of which portions of a page necessitate various JavaScript versions. This can be utilized to either weed out unnecessary components from bundles or include them in specific areas, streamlining the code for better performance.

Deferring the loading of unneeded components until they are necessary can considerably enhance page loading times, despite ingesting the same quantity of code on a website. This is due to the fact that not all of the code is practically processed and executed, therefore reducing the general strain on the system.

Experiencing a marked decrease in a page’s load time is probable if the dynamic content of a page is contingent on a complex library. To prevent this potential hindrance, it is best to load the dependencies only when the dynamic element is put into use.

For making a favourable impression on visitors, studies have proven that web pages ought to load within three seconds. This factor has grown in importance in large React applications, where code splitting is frequently utilized, since speed has a significant effect on user retention. Even a slight reduction in loading time can make a substantial difference.

How can you divide bundles in React?

Code-splitting is a potent feature of React that empowers developers to streamline their applications by loading only the code required to render a specific page. This results in better overall performance and user experience since the app only downloads the code it needs to display a page. Different methods of code-splitting in React are available, depending on the bundler utilized. Despite bundler choice, developers maintain complete control over the bundling process. One frequently employed technique of code-splitting in React is through webpack bundle splitting, which separates webpack bundles into individual components, allowing for more efficient code loading. Let’s delve into React bundle splitting and discover how it can benefit developers.

  1. Flexible Imports

    React simplifies code separation through its dynamic “import” syntax. Some bundlers can process dynamic import statements directly, while others require pre-configuration. This syntax can be used for server-side rendering as well as static site building.

    The dynamic nature of dynamic imports allows any component to function as a Micro Frontend without requiring the entire framework. Various resources are available to aid in the development, updating, and deployment of an individual component.

    The component’s development process may be distinct from the application intended to host it. Bit’s Compositions feature advocates for both manual and automated integration testing to guarantee the success of any future integrations.

    The “then” method is used with dynamic imports to bring in only the required code. Use the then function to reference this code.

    A single group can be divided into smaller segments, as shown below:
    • The primary objective of the initial segment is to lay the foundation for the primary route.
    • The remaining portions of the code are the ones that have not been employed.

      By implementing dynamic imports, supplementary data can be loaded asynchronously, which implies that only specific program components are loaded when a button is triggered. This results in more efficient loading times, as well as more control over the utilized resources.
  2. React.lazy

    React.lazy can often be used to delay the import loading process. While it lacks server-side rendering capability, it compensates for this deficiency by offering a wide range of other features.

    The fallback prop provided by the Suspense component can be used to display React elements until the component is fully loaded. The Suspense component should be placed in any available slot above the specified ‘slack’ one.

    React.lazy allows for dependencies to be imported dynamically as components and rendered on-demand. This functionality necessitates the embedding of the desired component within another component that will display a fallback if the dynamic import fails.

    While it is not required to provide the precise wording of any error messages, a specialized component called an Error Boundary must be used to handle content errors. For optimal presentation, the Error Boundary should be situated above any dynamically loaded components.

    The degree to which unauthorised users are prevented from accessing the requested code or functionality, and the frequency with which the requester uses them, are both critical factors to consider. Taking these steps not only improves the user experience but also reduces the initial loading time.
  3. Route-based Code Division

    Arranging your React code into separate components is a reasonable method to organize your application’s layout. As the user traverses the application, these components should be loaded automatically. Webpack offers the capability to create and serve code chunks in an efficient manner.

    Using the import() method in a dynamic language to import the required code produces an asynchronous component.

Pause for First Plagiarism Check

React’s built-in lazy loading and Suspense API provides a convenient means of segmenting code without the requirement of installing an extra third-party package. To transform application route components into lazy loading components, wrap them in a React.Suspense component. This enables the application to load components dynamically as needed, resulting in enhanced performance and lower memory usage.

Does Separating Your React Code Enhance Its Speed?

JavaScript reduces website speed in two phases:

  • Regarding page loading time, bigger bundles are less optimal.
  • Large bundles require more time to parse and compile, which delays the JS startup procedure.

If the bundle size of a program is excessively large, it can have a negative impact on loading, rendering, and scrolling performance, particularly for users with a slow or unreliable network connection, a low-power Android device, or a device with a low battery.

React’s code splitting feature empowers developers to produce an optimal user experience irrespective of the user’s device or network speed. By employing caching, compressing, and minifying script resources, file size can be reduced while maintaining the same output. This approach results in faster loading time, improved performance, and an overall better user experience.

Advantages of Code Separation

Some of the advantages of code separation are:

  • Reduced data is available for downloading and analysing, resulting in a much faster Time-to-Interactive.
  • A browser may decide when to load different sections of a program based on where they are placed on the computer’s hard drive.
  • Administrators may exclude administrative program code to reduce file size and protect sensitive data from ordinary users.
  • Client-side caching can be improved by updating only the required components of the program.

Code separation has some disadvantages.

Naturally, similar to every technology, there are certain drawbacks associated with React code separation.

  • Code separation requires additional data downloads after page initialisation without your knowledge.
  • If the user loses their internet connection, they will be unable to download any additional modules. In such cases, it is critical to alert or notify users so that they are aware of the issue and can take the appropriate action to remedy it.
  • Extra logic may be loaded with multiple modules, but this is only required in specific circumstances.
  • Every bundle requires an associated header file to be inserted into the application.
  • Thus, if more code is loaded together (especially when the website or page is loading for the first time), there may be a delay.

Getting Started with React Code Separation

To compare them in this case, we will utilise React Suspense and laziness separately.

Step 1: Create a new React app using the npm create-react-app command.

Step 2: To get started, enter the following command in the terminal from the primary project directory to launch the application.

Step 3: In App.js, we will include an input field for users to input information. Based on the type of argument passed in, this information will be utilised to display either the admin or client view via Home.js.

As already discussed, we intend to utilise both methods for lazy loading. The steps involved in the process are as follows:

Creating suspense using React Suspense (React 16.6+).

React now provides support for lazily loaded components with the introduction of the React Suspense feature in version 16.6.

React Suspense with Negative Response

The Suspense component may not be available to you if you have not upgraded to React 16.6 yet. To take advantage of this feature, we suggest that you upgrade to the most recent version. However, if you do require this component but are unable to upgrade at the moment, you can consider creating your own React Suspense component utilising Higher-Order Components (HOCs).

As online applications become more widely accessible, the number of JavaScript files required to display a webpage effectively continues to grow. As a result of this growth, the webpage size also increases. If you are familiar with popular JavaScript libraries such as Axios, React, Lodash, Vue, or jQuery, you are aware of how these libraries can substantially contribute to the size of a webpage.

To address this situation, incorporating webpack bundle splitting into your codebase is widely recommended. React code splitting based on routing and dynamic imports is only two of many potential options to consider (with lazy loading being one of them). It is advisable to concentrate on developing a code-splitting solution specific to your React project. This is a comparatively easy-to-set-up and maintain procedure that is reliable in all scenarios, even when utilising routing. Nonetheless, there is one exception to this approach that will be discussed in the final section.

There are various reasons why developers choose to split their code package into multiple components, such as enabling the parallel loading of those components. In doing so, the application loading process accelerates, which leads to a reduction in waiting time for the end-users, consequently improving their experience.


  1. How Code Splitting Works in React.js?

    Code splitting refers to the process of dividing a large piece of code into smaller, more manageable sections that can be loaded when necessary. This technique can be helpful in improving the performance of software applications while also making maintenance and debugging more straightforward. By breaking the code into smaller chunks, issues become easier to identify and rectify, and new features can be added or updated more easily. Additionally, it can reduce the initial loading time of a program, as only the necessary portions of the code are loaded when required.

    As a program’s source code grows in complexity, it can lead to a proliferation of JavaScript files and bloat from external libraries.

    A developer may choose to break the code down into smaller segments to reduce the need for multiple downloads. This approach, known as lazy-loading, is favoured by programmers because it only loads the required files, improving the performance of the page or application when users interact with it.

    Even though the code is the same, only the essential parts are executed when the website first loads.

    Code splitting is a technique that developers use to divide their application’s source code into separate independent bundles. This can be achieved through bundlers like Webpack and Browserify, which break down the entire program into individual modules at runtime. This technique improves the overall performance and scalability of the application.
  2. Why is “Bundle Splitting” Necessary?

    By dividing a package into two separate parts, you can reduce its overall size. This reduction will enhance the time it takes for your application to be activated and decrease the payload size required by your program.

    Bundles are useful for minor development tasks, but the bundle size will increase as your application size grows. This includes third-party libraries that have been incorporated into the program. When incorporating these libraries into an application, it’s critical to monitor the bundle size to ensure that the loading time remains reasonable. Failure to do so might result in prolonged loading times.

    If you frequently encounter issues like these with your big bundles, you should consider breaking up the bundle.

    Bundlers like Webpack and Browserify, which enable code-splitting and the formation of smaller bundles, are just two of the several options available, allowing for dynamic loading at runtime. This feature can significantly improve application functionality.
  3. An Overview of Code Splitting Methods

    Breaking down a single, large source code file into smaller bundle files is an efficient technique known as JavaScript code splitting. Instead of consolidating all of the code and dependencies into a single file, developers can divide the source code into smaller, more manageable chunks. This can enhance application performance by reducing the amount of code that must be downloaded and parsed before rendering the application. Furthermore, code splitting facilitates codebase maintenance by organising the source code into logical units.

    Upon running the bundle at the app’s entry point, React Native will load the chunked files as required.

    Code splitting refers to the practice of dividing an application’s source code into numerous files that don’t depend on one another. This allows specific code sections to load on demand when required, advancing the program’s initial loading time while reducing its memory consumption.

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