mattpodwysocki

function *flatten<T>(iterable: Iterable<T>, depth: number = Infinity): Iterable<T> {
  if (depth === 0) { return iterable; }
  
  for (let item of iterable) {
    if (typeof item[Symbol.iterator] === 'function') {
      yield *flatten(item, depth - 1);
    } else {
      yield item;
    }
  }

iansinnott

/**
 * Read the text contents of a File or Blob using the FileReader interface.
 * This is an async interface so it makes sense to handle it with Rx.
 * @param {blob} File | Blob
 * @return Observable<string>
 */
const readFile = (blob) => Observable.create(obs => {
  if (!(blob instanceof Blob)) {
    obs.error(new Error('`blob` must be an instance of File or Blob.'));
    return;

justinwoo

// install @types/react-redux and other nonsense

import * as React from 'react'
import { connect } from 'react-redux'
import { YourActualAppState } from './wherever-it-is.ts'

export function mapStateToProps({
  whatever
}: YourActualAppState) {
  return {

alexandru

#!/usr/bin/env node

import { IO, Try, Success, Failure, Either, Left, Right, Cancelable, Duration } from "funfix"
import { RequestResponse } from "request"

import * as fs from "fs"
import * as request from "request"
import * as Url from "url"
import * as cheerio from "cheerio"
import * as minimist from "minimist"

rupertlssmith

module GameState
    exposing
        ( Game(..)
        , GameDefinition
        , PlayState
        , loading
        , updateGameDefinition
        , updatePlayState
        , updateScore
        , toReady

joeporpeglia

import React from 'react';
import Counter from './counter';

const mapProps = ({ state, dispatch }) => ({
    count: state,
    increment: () => dispatch({
        type: 'increment',
    }),
    decrement: () => dispatch({

bvaughn

Profiler

React 16.4 will introduce a new Profiler component (initially exported as React.unstable_Profiler) for collecting render timing information in order to measure the "cost" of rendering for both sync and async modes.

Profiler timing metrics are significantly faster than those built around the User Timing API, and as such we plan to provide a production+profiling bundle in the future. (The initial release will only log timing information in DEV mode, although the component will still render its children- without timings- in production mode.)

How is it used?

Profiler can be declared anywhere within a React tree to measure the cost of rendering that portion of the tree. For example, a Navigation component and its descendants:

bvaughn

This API was removed in React 17

---

Interaction tracing with React

React recently introduced an experimental profiler API. After discussing this API with several teams at Facebook, one common piece of feedback was that the performance information would be more useful if it could be associated with the events that caused the application to render (e.g. button click, XHR response). Tracing these events (or "interactions") would enable more powerful tooling to be built around the timing information, capable of answering questions like "What caused this really slow commit?" or "How long does it typically take for this interaction to update the DOM?".

With version 16.4.3, React added experimental support for this tracing by way of a new NPM package, scheduler. However the public API for this package is not yet finalized and will likely change with upcoming minor releases, so it should be used with caution.

bvaughn

React recently introduced an experimental profiler API. This page gives instructions on how to use this API in a production release of your app.

Table of Contents

• Profiling in production
  • Create React App
  • Webpack 4

Profiling in production

React DOM automatically supports profiling in development mode for v16.5+, but since profiling adds some small additional overhead it is opt-in for production mode. This gist explains how to opt-in.

dsherret

// this could be improved... (ex. ignore interfaces/type aliases that describe a parameter type in the same file)
import { Project, TypeGuards, Node } from "ts-morph";

const project = new Project({ tsConfigFilePath: "tsconfig.json" });

for (const file of project.getSourceFiles()) {
    file.forEachChild(child => {
        if (TypeGuards.isVariableStatement(child)) {
            if (isExported(child))
                child.getDeclarations().forEach(checkNode);