Javi Velasco

2019

ReactiveConf

The monorepo odyssey

At ZEIT I'm in charge of the Now CLI, the easiest and simplest way to deploy serverlessly to the cloud. Just execute now against any directory or file in the filesystem, and a deployment is instantly made to our global network.
The main program and its subcommands query our different API endpoints (https://zeit.co/api). For example, when creating a deployment we first upload all its files (File Upload API), followed by deployment creation (Deployment API) and then we ensure it can run for the first time (Instances API).
Errors can occur at any stage of this pipeline: network errors, transient API failures, failed API validations or requirements, rate limiting due to too many requests, among many others.
This talk describes how we modeled our error-handling system for asynchronous operations using Flow, in order to: 
- Provide a scalable system that allows us to grow our API and subcommands as our business quickly evolves 
- Ensure that the developer is aware of the entire error space for each operation they perform by leveraging the type system (e.g.: no unknown exceptions) 
- Provide accurate and easy-to-understand error messages in combination with https://err.sh hyperlinks

2018

Modeling errors in Now CLI

React Alicante

2017

Styling Components for React UI Kits

React is a wonderful tool to write reusable components but there is no clear definition on how a good API for theming and customization should look like. There are too many approaches when it comes to styling, and choosing one of those is a crucial decision, specially for vendor component libraries like http://react-toolbox.com/

In this talk we will go through some of the most important styling libraries, analyzing what should they cover from the point of view of a library of components, and using React Toolbox as study case. We will explore how customization and theming can be modeled for UI Kit projects with different tools. 

Finally, we will see a simple technique that allows one to write components that are agnostic from styling, without committing to an specific tool. This makes possible to switch between styling strategies over time and experiment with them while keeping the same component implementation.

ReactJS Day

React is a wonderful tool to write reusable ui components but it takes no decisions on how they should be styled. This leads to a huge amount of different styling approaches, most of them based on CSS in JS, that usually introduce some coupling with your code.

Is it possible to skip this dependency and to write components that doesn't depend on style? In this talk we will go through some of the most interesting approaches made by styling libraries, analyzing what should they cover to make components highly reusable and customizable. Eventually we will see a technique that the upcoming React Toolbox Core is going to use to ship complex components agnostic from style. We will see how really complex components like DatePickers can be reused and re-styled even for React Native.

Writing highly reusable React components

Recently I wrote a small package called react-css-themr, which allows you to separate styles from components, plus an easy API to compose and inject styles. Currently I’m migrating React Toolbox to this approach and, although I don’t know yet how this will it work, I’m sure it’s gonna change how we handle styling for vendor components, making easier to customize this and any other library.
I would like to tell you how it went in a lighning talk at Reactive 2016, dropping some thoughts about styling components in React. Star this gist if you want to give your support!

https://gist.github.com/javivelasco/1a095a673c221bc5c69246a4519b353a