Javascript’s Bundler Overview
Let’s start by defining a JavaScript bundler. A JavaScript bundler is a program that compiles all of your code and its dependencies into a…
Javascript’s Bundler Overview
Let’s start by defining a JavaScript bundler. A JavaScript bundler is a program that compiles all of your code and its dependencies into a single JavaScript file that is ready for production and can be loaded into a browser. Also, when working with libraries that have numerous dependencies or when your project grows too big for a single file, you can utilize a JavaScript bundler. The fact that a bundler creates a dependency graph as it navigates through your first code files is a terrific feature. This indicates that the module bundler keeps track of both the dependencies of your source files and the requirements of third parties starting from the entry point you selected. This dependency tree ensures that all source code files and related files are kept up-to-date and free of errors.
The next question to ask is why would we want to use bundlers.
JavaScript hasn’t had a standard for requesting dependencies from your code historically. Older versions of browsers did not understand the modern es6 style of writing javascript code. Es6 style of coding came with features such as “import”, “export” or “require”, arrow functions, JSX, etc. So basically, the bundler bundles all your code into one single file and sends it down to the browser in a way that it would understand your code.
If you wanted to write a javascript code for a weather web app in the past, for instance, your code would look like this:
<head>
<script src="//code.jquery.com/jquery-1.12.0.min.js"></script>
<script src="/js/navbar.js"></script>
<script src="/js/weatherapi.js"></script>
<script src="/js/main.js"></script>
<script>
// Here goes some code
</script>
</headBut now, while utilizing a bundler, the files and their dependencies will be combined into a single file, like this:
<head>
<script type="text/javascript" src="/bundle.js"></script>
</headFrom the above example, it is easy to see why bundlers are very useful. The code above is much easier to read and understand.
Below are some advantages of using bundlers:
- Many popular module bundlers come with performance optimization features that make your code respond fast on the browser.
- They offer a consistent tooling environment that relieves you of the burden of dependencies.
- Bundlers offer features that boost productivity, such as robust error reporting that makes it easy for programmers to identify and correct issues.
- We can use npm since require() and exports are implemented similarly to Node.js and look for dependencies in the “node modules” directory. On this basis, you can quickly install and publish new libraries and take advantage of the versioning capabilities of npm.
- Some bundlers remove unnecessary code from the final file, leaving only the code your application requires to function.
There are different types of bundlers but I will only talk about parcel and webpack.
Parcel
Parcel bundler is a fast build tool that allows developers to configure modules (Js, CSS, and HTML) necessary for development. It is the second most popular bundler, behind webpack.
To get started, run **npm i parcel**.
Let’s say you have a sample HTML boilerplate:
<html>
<body>
<script src="./index.js"></script>
</body>
</html>After that, run **parcel index.html** to utilize Parcel to create the HTML file.
Pros
- Zero configuration
Parcel solves the configuration issues faced with Webpack and Browserify providing developers with a performant architecture needed for rapid web development. There’s also multi-asset support like Webpack enabling bundles for all kinds of non-JavaScript assets like CSS, HTML, and images.
- Fast
Parcel is fast providing premium resource optimization features like hot module replacement and lazy loading of split code. According to the most recent benchmarks, Parcel’s bundling speed is 9.98s, compared to Browserify’s 22.98s and Webpack’s 20.71s. Using Parcel’s built-in caching technique can even deliver quicker results, with a benchmark time of 2.64s.
- Asset optimization
Features like code-splitting allow you to break code files into chunks, thereby reducing load time.
Cons
- Lack of advanced customizations
As a highly-opinionated bundler, Parcel is perfect for small and medium-sized applications. Nonetheless, making it work for complex applications where you need to modify the configurations might be tedious. In this situation, most developers prefer to use Webpack.
Webpack
Webpack functions as a transformer, minifier, and optimizer of all types of file resources and assets as well as a static module bundler for JavaScript files thanks to a wealth of advanced and highly customizable features. Not only that. The ecosystem of plugins and loaders for Webpack is also fairly robust.
Getting started is as simple as running **npm i webpack**
Pros
- Multi-resource support
In addition to providing out-of-the-box support for JS files, Webpack has a rich Plugin ecosystem it relies on to bundle other files like CSS and Images.
- Asset optimization
Features like code-splitting allow you to break code files into chunks, thereby reducing load time. There’s the Hot module replacement that helps you to manage modules without fully reloading the browser. Developers can employ Loaders in preprocessing their files, resulting in a faster app runtime. These and more highly customizable optimization features have made Webpack the most popular JS bundler.
- Developers’ productivity
When working with a complicated task like Module bundling as a developer, it’s crucial to have:
- Extensive documentation.
- A solid ecosystem of third-party tools you can lean on.
- Efficient error debugging process that makes your work easier.
These three needs are met by Webpack, which provides a vast ecosystem of plugins and loaders as well as source map-powered debugging. Not just that. The core caching technique of Webpack enables programmers to create apps quickly.
Cons
- Complex
Numerous developers who have a love-hate relationship with Webpack find its complexity to be a double-edged sword. It also has a difficult learning curve and is sophisticated.
- Buggy and Slow
Webpack’s all batteries included approach can sometimes cause Webpack app integrations to be over-engineered. Over-reliance on plugins to do simple functions can cause the bundler to slow W necessitating technical debugging to make it well-optimized.
- In a way, not suitable for learners
Webpack in a way is good for learners because it just gives you all the tools you need to code without necessarily configuring anything. One line of command and you get all you need. Why I will say it's not suitable for learners is because using that one line of command kinda drops you“ in the middle of your project”, you would not know how you got there or how these packages work “under the hood”. This is opinionated anyway.
Start using a JavaScript bundler today. Check out parcel or webpack.
Inspired by Brian Holts from frontend masters.
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