andrewk

Spies

Create a spy

// "bare" spy
var spy = jasmine.createSpy('spyName');

// Mock object of spies: spy.next(), spy.current(), etc

wincent

2015-01-29 Unofficial Relay FAQ

Compilation of questions and answers about Relay from React.js Conf.

Disclaimer: I work on Relay at Facebook. Relay is a complex system on which we're iterating aggressively. I'll do my best here to provide accurate, useful answers, but the details are subject to change. I may also be wrong. Feedback and additional questions are welcome.

What is Relay?

Relay is a new framework from Facebook that provides data-fetching functionality for React applications. It was announced at React.js Conf (January 2015).

Rich-Harris

Stuff I wish I'd known sooner about service workers

I recently had several days of extremely frustrating experiences with service workers. Here are a few things I've since learned which would have made my life much easier but which isn't particularly obvious from most of the blog posts and videos I've seen.

I'll add to this list over time – suggested additions welcome in the comments or via twitter.com/rich_harris.

Use Canary for development instead of Chrome stable

Chrome 51 has some pretty wild behaviour related to console.log in service workers. Canary doesn't, and it has a load of really good service worker related stuff in devtools.

OliverJAsh

/*

In JavaScript, objects can be used to serve various purposes.

To maximise our usage of the type system, we should assign different types to our objects depending
on the desired purpose.

In this blog post I will clarify two common purposes for objects known as records and dictionaries
(aka maps), and how they can both be used with regards to the type system.

chrislopresto

import * as React from 'react';
import { theme } from './theme';
import { ThemeProvider, createGlobalStyle } from './styled-components';

const GlobalStyle = createGlobalStyle`
  body {
    font-family: Times New Roman;
  }
`;

swyxio

// create context with no upfront defaultValue
// without having to do undefined check all the time
function createCtx<A>() {
  const ctx = React.createContext<A | undefined>(undefined)
  function useCtx() {
    const c = React.useContext(ctx)
    if (!c) throw new Error("useCtx must be inside a Provider with a value")
    return c
  }
  return [useCtx, ctx.Provider] as const

sbadulin

function iconTemplate({ template }, opts, { imports, componentName, props, jsx }) {
  const typeScriptTpl = template.smart({ plugins: ['typescript'] });
  return typeScriptTpl.ast`
    ${imports}
    import styled, { css } from 'styled-components';

    const SvgIcon = (${props}: React.SVGProps<SVGSVGElement>) => (props => ${jsx})({className: props.className});

    const ${componentName} = styled(SvgIcon)([],
      ({ theme, fill, width }) => css\`

sebmarkbage

I heard some points of criticism to how React deals with reactivity and it's focus on "purity". It's interesting because there are really two approaches evolving. There's a mutable + change tracking approach and there's an immutability + referential equality testing approach. It's difficult to mix and match them when you build new features on top. So that's why React has been pushing a bit harder on immutability lately to be able to build on top of it. Both have various tradeoffs but others are doing good research in other areas, so we've decided to focus on this direction and see where it leads us.

I did want to address a few points that I didn't see get enough consideration around the tradeoffs. So here's a small brain dump.

"Compiled output results in smaller apps" - E.g. Svelte apps start smaller but the compiler output is 3-4x larger per component than the equivalent VDOM approach. This is mostly due to the code that is usually shared in the VDOM "VM" needs to be inlined into each component. The tr

shilman

NOTE: This was written in 2020 and has been superseded by docs at storybook.js.org

Storybook React props handling for Typescript

We've flip-flopped on prop table handling for React components written in Typescript. This document attempts to be a final reference for anybody who's been trying to follow along.

TLDR:

SB6 uses react-docgen-typescript by default. We hope to use react-docgen in SB7. The whole experience led to zero-config in SB6, so it's now a one-line change main.js to switch between the two.