Which is the Best Module Bundler? Webpack vs. Rollup vs. Parcel.

 In this blog post we will look that which is the Best Module Bundler? Webpack vs. Rollup vs. Parcel. Every module bundler is having some advantage and some disadvantage but in this blog we will look that which is going to be best module bundler for your projects.

Let's have a brief intro about Module bundle ? Who are newcomers.

Module Bundler :- 
    A module bundler is a tool that takes pieces of JavaScripts module and their dependencies and bundles them into a single file.

When we write our code in modular patterns:- 

• We keep our javascripts in separate file and folder bases on their functionality.
• Add the script tag for each file that we are using in correct order of dependencies.

For each script tag server will send the request to the server and which will tends to the bad performance of you application. In order to overcome such issue we simple create a single bundle file which will integrate all the other files and that bundle file will be send to server.

Why we should use Module Bundler ?:- 

    There are many advantage of Module bundler that makes everything done for your in no time.

Let's have a look on them:- 

    1. Minified your code :- Bundle can also minified your code by removing unnecessary white spaces, new line, comments and block delimiters without affecting .

let's take a example and try to understand it:-   

var arr = [];
for (var index = 0; index < 50; index++) {
  arr[index] = index;
}

  

here we just create an array and initialized it with 1-100 value.  After minifying the above code. It will look like this.

for(var arr=[index=0];++index<20;arr[index]=index);

The extra spaces and line has been remove from the code, You might say this code is not readable. But minified code is easy to fetch and interpret by the browser. Which can helpful to increase loading speed of the application.

    2. Code Splitting :-  Code-splitting makes it possible to break your app apart into manageable chunks that can be loaded on-demand, meaning your users get an interactive site much faster than if they had to wait for the whole application to download and parse.

let's take a example and try to understand it:- 

           let suppose you have a website that is having multiple component of javascript code. In Your home page your website is having a form.

So now here is a question for you , Is it necessary to load javascript code of form validation when your home page is reloading?

Obviously your answer will be  NO.

So here module bundler gives you the access of doing this. Only that party of javascript code will be loaded in the html which is currently required.

    3. Live-Reload :-  Module bundler gives you the live reload functionality while working on development phase of your application that is very help full to boost your working speed.

    4. Transformation :- Module bundlers require javascript files to create a bundle. They cannot process any other format directly. So, in order to process files other than javascript , we need to first convert that format into javascript then we will pass it to the bundler. This process of conversion is called transformation.

    5. HMR (Hot Module Replacement) :- Hot module replacement (HMR) improves the development experience by automatically updating modules in the browser at run time without needing a whole page refresh. HMR only refresh the segment of page on which you are currently working.

    

    6. Static assets :- Static assets such as images and CSS can be imported into your app and treated as just another node in the dependency graph. No more carefully placing your files in the right folders and hacked-together scripts for adding hashes to file URLs . These all headache is done for you by the Module Bundler.

You can do these all things manually. But well.... Good luck.

Difference Between Webpack , Rollup and Parcel :- 

    Now let's have comparison between webpack vs. Rollup vs. Parcel.

We will be doing these comparison on the basic of some of the feature of a module bundler and we will check it out that which module bundler provide a better accessibility of a functionality.

1. Dead Code Elimination :- 

Dead code elimination, or Tree shaking, as it’s often called, is very important to achieve the optimum bundle size and hence application performance.

Here Parcel win the race of this functionality, Parcel is having better support for ES6 and CommonJS modules.. This is wide-ranging since most of the code in libraries on npm still uses CommonJS.

Rollup got the second place in the race of this functionality, it statically analyzes the code you are importing and will exclude anything that isn’t actually used. That's why you required less configuration for your application.

And Now Wepack, It require more effort for configuration from your end to use/enable Dead Code Elimination.

• You need to add a minifier that support Tree Shaking,
• You also need to set the SideEffects flag in your package.json file. 
• Read more about Tree Shaking

2. Code Splitting :- 

       

     Rollup has recently added experimental code splitting feature. Split chunks created by rollup are themselves just standard ES modules that use the browser’s built-in module loader without any additional overhead. We need to set experimentalCodeSplitting and experimentalDynamicImport flags to true in the config.js file. learn more about Rollup code Splitting.

Parcel supports zero configuration code splitting. Here code splitting is controlled by use of the dynamic import() function syntax proposal, which works like the normal import statement or require function, but returns a Promise. This means that the module is loaded asynchronously. Learn more about Parcel Code Splitting.

Code Splitting is the most compelling feature of webpack. There are three general approaches to code splitting available in webpack:

• Prevent Duplication: Use the CommonsChunkPlugin to dedupe and split chunks.
• Dynamic Imports: Split code via inline function calls within modules.
• Entry Points: Manually split code using entry configuration.
• Learn more here about Webpack code splitting.

3. Configuration :- 

Here Parcel win the race of this functionality, parcel doesn't require any config file. Just install the parcel and run the build . Parcel will do everything for you in no time.

Webpack and Rollup both require a config file specifying entry, output, loaders, plugins, transformations, etc. However, there’s a slight difference between webpack and rollup config.js file.

• Rollup has node polyfills for import/export, but webpack doesn’t.
• Rollup has support for relative paths in config, but webpack doesn’t — which is why you use path.resolve or path.join.

4. Transformation :- 

    Parcel supports various transformations like css, scss , images etc without config file. Parcel automatically runs these transforms when it finds a configuration file (e.g. .babelrc, .postcssrc) in a module.

    Webpack uses loaders of different formats for transformation. eg: style-loader, css-loader for css files. We need to configure the file type and corresponding loader to be used in it’s config file.

    Rollup uses plugins for transformation. We need to specify the plugin in the rollup config file.

5. HMR (Hot Module Replacement) :- 

    

Parcel has built-in support for hot module replacement.

Rollup doesn’t do hot module replacement (HMR).

Hot Module Replacement is one of the most useful features offered by webpack. It allows all kinds of modules to be updated at runtime without the need for a full refresh. webpack-dev-server supports a hot mode in which it tries to update with HMR before trying to reload the whole page.

So finally we have a conclusion on the basic of above comparison :- 

• If you are building a basic application and want to get it up and running quickly, then go for parcel.
• If you are building a library with minimal third-party imports, then go for Rollup.
• And If you are building a complex application with lots of third-party integrations? Need good code splitting, use of static assets, and CommonJs dependencies? Use webpack.

At the end of this blog I just want to say that choose a module bundler on the basic of your project requirement not what people say. You would be well known with your project and its requirements. So choose it wisely.

Thanku 

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