React

“”React was invented by Jordan Walke, who was working on Facebook Ads at the time. He changed teams to Product Infra to focus on React full-time and we launched a React version of the liking and commenting UI as the first step to using React on the main Facebook website. By that time, Instagram had joined Facebook and a former Facebook Photos engineer, Pete Hunt, joined the Instagram team and built the first version of Instagram's feed on web using React. Since Instagram's code base was separate from Facebook's, this endeavor required extracting React from Facebook's code base so that Instagram could use it. In this sense, Instagram was the first "external" user of React.

— James Ide (24 Nov, 2015) Medium

“”One of the first projects that React was used for was the UFI, the Universal Feedback Interface. Which is basically the likes, comments and shares at the bottom of each post. Newsfeed had a billion people hitting it every day and was massively tuned for performance. On the input side of course you're like clicking it to add likes, you're typing into it to add comments, but also on the receiving side we want comments to come in live. So as you're looking at it as a comment comes in, we want it to just pop up right there. And there was this product desire for that interface to fell almost like a one-off chat thread. --- Instagram joined Facebook in 2012. There was a couple of engineers from Facebook that went to join Instagram to help them expand the product offering. At the time Instagram was just an iOS and an Android app and they wanted to have a web presence as well. One morning the photo's team got called into the office early. They said like be at HQ at 8am and then the VP of engineering was like, "Hey, we bought Instagram, they're your new co-workers now." And that's kind of where React enters the picture. That ended up shipping on Instagram.com, which was the second use of React in production ever and the first use of building a full application end to end in React. We had to take this thing that was very much tied to Facebook's infrastructure, which back then was a big giant PHP application. --- On the pro side of React, it handles complexity, way, way more. Even when writing the ads creation flow in Bolt we had already hit one place that you just could not do in Bolt without writing spaghetti code. --- It was a really humbling experience. It was kind of a letdown for us because we had worked nights and weekends on getting this thing open sourceable and then we go to launch it, everyone hated it. The thing that everyone focuses on is that people really hated JSX. This is the slide for sure. We haven't talked about any problems we're trying to solve, we haven't talked about why this is working for us or what were the principles of design. We're just like, boom, here's some XML in your JavaScript and people are like, hey what is happening. --- He was literally creating Redux in service of being able to deliver this talk. I called it presentation driven development because the thing that shook out of it was you know this sort of like canonical state management library for React apps for several years.

— Honeypot (February 11, 2023) "React.js: The Documentary"