Ladle: The Story About Modules and Performance

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The bigger they are, the slower it gets. I am talking about your applications and the bundling process. Fortunately, there might a be better future - the one without bundlers. This talk will be about JavaScript modules, Vite and how we built Ladle - a speedy tool for your React stories.

Vojtech Miksu
Vojtech Miksu
16 min
24 Oct, 2022

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Video Summary and Transcription

Hello everyone, my name is Wojta Mikšu. I work at Uber as a web infrastructure engineer. Today, I will tell you about a new open tool that supercharges developing and testing your React components. This talk covers the history of JavaScript modules, the introduction of Vite and Ladle, and future predictions. Ladle is an open-source tool built on top of Vite for developing and testing React components through stories. It offers features like different viewports, component variations, event handler logging, theme switching, and more. Ladle has received positive feedback and shows improvements in dev server startup and hot module replacement.

1. Introduction to Open Tool for React Components

Short description:

Hello everyone, my name is Wojta Mikšu. I work at Uber as a web infrastructure engineer. Today, I will tell you about a new open tool that supercharges developing and testing your React components. This talk has 4 sections. The first is a short history lesson about Javascript features we've been missing. Then we talk about Javascript modules, Vite, and Ladle. Finally, we will wrap this up with some future predictions. JavaScript was missing a concept of modularization. Node.js adopted CommonJS, but it has weaknesses for browsers.

Hello everyone, my name is Wojta Mikšu. I work at Uber as a web infrastructure engineer, and today I will tell you about a new open tool that supercharges developing and testing your React components.

This talk has 4 sections. The first is a short history lesson about Javascript features we've been sorely missing for a long time. Then we talk about Javascript modules, also known as ES6 modules or ESM. The third section introduces Vite, a new type of bundler, followed by an introduction of Ladle, a tool we built on top of Vite. And finally, we will wrap this up with some future predictions.

Do you remember what 1995 browsers looked like? I don't, but they were very different for sure. It's not surprising that JavaScript was missing some features when it was introduced. The one feature that's relevant to this talk is the way how JavaScript is loaded into browsers. You have to use the script tag. The code itself can be inlined or point to a file. This was fine 15, 10 years ago when JavaScript was used to add a bit of interactivity. But when we build modern frontend applications, it causes some serious issues. The files are loaded and executed synchronously and their order matters. Top level variables end up in the global scope, so it's easy for two unrelated libraries to cause naming collisions. Every time you create a new file, you have to load it through an additional script tag and bind it through the global scope. There's no easy way to eliminate unused code either.

JavaScript was missing a concept of modularization. This was especially a big problem for server-side JavaScript known as Node.js. Some better system for splitting and encapsulating code was badly needed. So, Node.js adopted CommonJS. This syntax should be very familiar to anyone that touched JavaScript in recent years. It addresses a lot of issues, but not all of them. It introduces a concept of code providers and consumers. It's also a whole philosophy and it was used to create the biggest package registry for code sharing called npm. It enables dynamic code loading. However, there are some major weaknesses that make it unusable for browsers. For example, there are file system references like the usage of dirname. But the biggest issue is that module resolution and loading needs to be done synchronously.

2. Introduction to JavaScript Modules and Vite

Short description:

CommonJS was a better system than JavaScript ever had, allowing developers to split code into modules without worrying about browser support. JavaScript modules were introduced as an official standard, supported by all modern browsers and runtimes. They work asynchronously, load additional modules when needed, and can be easily tree shaken. Despite some compatibility issues, it's clear that JavaScript modules are the future. Vite is a new development environment that takes advantage of unbundled JavaScript modules, resulting in instant dev server startup. Vite uses ESbuild and Rollup plugins to convert existing libraries from CommonJS and remove unnecessary dependencies like JSX and TypeScript.

That would block rendering in browsers and lead to really bad experiences. CommonJS was developed independently from the ECMAStandards party, so it never became the core part of JavaScript. However, it was still a better system than JavaScript ever had, and developers wanted to use server code in their frontend applications. So the bundlers like Webpack were introduced. Webpack can analyze and resolve all CommonJS modules before creating a single bundled file that serves two browsers. This was a big win-win. Developers can use CommonJS to split code into modules and don't have to worry about browser support in it.

But we were still missing an official standardized way that would work in browsers and other runtimes without additional tooling. JavaScript modules were introduced. Today, they are supported by all modern browsers and runtimes. You can load them by setting the type attribute to module. And the best part is that browsers understand import-export syntax and load additional modules when needed. Modules work asynchronously and don't prevent pages being interactive. There's a promise API to import modules dynamically. The code can be easily tree shaken. Only the bits you use need to be loaded. It works everywhere across all browsers and environments. And it is an official standard now.

Don't get me wrong. There are still some issues when it comes to compatibility with common JS and existing ecosystem, so the adaption can be sometimes cumbersome. However, it's clear that this is the future of JavaScript.

So what is Vite? It's a new development environment built on the fact that JavaScript modules don't need to be bundled before being served to browsers. It was a major and very slow part of Webpack. Therefore, the dev server startup can be instant. Some bundling and compilation is still needed. A lot of existing libraries need to be converted from common JS. We also need to remove things like JSX and TypeScript. Vite uses ESbuild and Rollup plugins for that. Let's compare Webpack and Vite startup process side-by-side. This is the old Webpack approach.

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