kddial

// source: https://stackoverflow.com/a/59843241
const usePrevious = (value, initialValue) => {
  const ref = React.useRef(initialValue);
  React.useEffect(() => {
    ref.current = value;
  });
  return ref.current;
};

mayank23

Jest Mock Any Property on Window Utility - with automatic cleanup.

jessebeach

class Grid extends React.Component {

  _timeoutID;
  
  constructor() {
    this.state = {
      isManagingFocus: false,
    };
  }
  

paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

brianmacarthur

var express = require('express');
var cookieParser = require('cookie-parser');
var session = require('express-session');
var flash = require('express-flash');
var handlebars = require('express-handlebars')

var app = express();
var sessionStore = new session.MemoryStore;

// View Engines

bendc

// array utils
// =================================================================================================

const combine = (...arrays) => [].concat(...arrays);

const compact = arr => arr.filter(Boolean);

const contains = (() => Array.prototype.includes
  ? (arr, value) => arr.includes(value)
  : (arr, value) => arr.some(el => el === value)

bclinkinbeard

Populating referenced collections in MongoDB from JSON files using Node.js and Mongoose

I recently began working with Node and MongoDB for a small personal project, largely just to learn the technologies. One thing that is fairly simple but that I found far from obvious and lacking in concrete examples was how to populate the part of my database that used referenced collections from the sample JSON data I was starting with. This post attempts to fill that gap using the following code snippets, which are heavily commented inline. You will notice I am using the awesome Mongoose library which makes working with MongoDB very easy.

http.createServer( app ).listen( app.get( 'port' ), function() {

    mongoose.connect( 'mongodb://localhost/{YOUR_DB_NAME}' );

	var db = mongoose.connection;