Daniel Torres danielfttorres

WTF Flow

[Flow][] static type checker is a wonderful attempt to bring [algebric data types][] to JS. It is still fairly new project and there for has few WTFs that can pull you down the rabbit hole. This document is attempt to document things that may seem like a WTF from the perspective of JS developer who tries to employ static type checker, or in other words, some items on the list may be very subjective & based on the background of the writer.

Polymorphic type that is a function

It is very likely that one will wind up using [Polymorphic functions][] to solve a more general problem. And if you define type alias for such a function you may be puzzled what is the right syntax should be used for such type definition.

Let's start with:

Shallow

Real unit test (isolation, no children render)

Simple shallow

Calls:

constructor
render

	import Relay, {
	RootContainer,
	Route
	} from 'react-relay'

	class SeasonRoute extends Route {
	static paramDefinitions = {};

	static queries = {
	currentSeason: () => Relay.QL`query { currentSeason }`,

	{ fontWeight: '100' }, // Thin
	{ fontWeight: '200' }, // Ultra Light
	{ fontWeight: '300' }, // Light
	{ fontWeight: '400' }, // Regular
	{ fontWeight: '500' }, // Medium
	{ fontWeight: '600' }, // Semibold
	{ fontWeight: '700' }, // Bold
	{ fontWeight: '800' }, // Heavy
	{ fontWeight: '900' }, // Black

	/**
	* Created by Awesometic
	* It's encrypt returns Base64 encoded, and also decrypt for Base64 encoded cipher
	* references: http://stackoverflow.com/questions/12471999/rsa-encryption-decryption-in-android
	*/
	import android.util.Base64;

	import java.nio.charset.StandardCharsets;
	import java.security.InvalidKeyException;
	import java.security.KeyFactory;

	/* global window */

	const popup = (url) => {
	const windowArea = {
	width: Math.floor(window.outerWidth * 0.8),
	height: Math.floor(window.outerHeight * 0.5),
	};

	if (windowArea.width < 1000) { windowArea.width = 1000; }
	if (windowArea.height < 630) { windowArea.height = 630; }

	import React from 'react';
	import {
	View,
	Text,
	} from 'react-native';
	import { TextInputMask } from 'react-native-masked-text'

	export default function maskedInputTemplate(locals) {
	if (locals.hidden) {
	return null;

	package main

	import (
	"bufio"
	"fmt"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/rekognition"
	"github.com/blackjack/webcam"
	"os"

	REACT NATIVE IOS vs ANDROID FONT USE

	Tested for React Native 0.41+

	IOS:
	- Place the fonts in the assets and make sure they are bundled along
	- On iOS, fontFamily in Text match the Font Family name as described in Font Book (macOS). Font weights can be specified exactly.

	ANDROID:
	On Android, there are two ways of using fonts:

	import React from 'react'
	import { AppRegistry } from 'react-native'
	import setup from './setup'

	AppRegistry.registerComponent('ReactNavigationTest', setup)