tincho

these are some samples of coding excercises I have resolved in past interviews

See also:

https://github.com/tincho/trivia-react-challenge

https://github.com/tincho/acme-panel

tincho

/*
why fixDate?
if we create a JS Date writing:
var d = new Date("2015-05-15")
we are not specifying any timezone
the browser/environment will asume it is UTC+000,
and always represent it in user's LOCAL TIMEZONE!
so, running in an environment located in a UTC-3 zone,
d would actually show 2015-05-14 at 21:00
and may lead to errors.

tincho

const combine = (...fns) => (...args) => fns.reduce((returnValues, fn) => [...returnValues, fn(...args)], [])

tincho

// alternative version using ES6 Array.from

const chunkify = (chunkSize, src) => Array.from(
  { length: Math.ceil(src.length/chunkSize) },
  (_, i) => src.slice(i * chunkSize, i * chunkSize + chunkSize)
)

tincho

// @params: N functions that should return an Object
// @returns a fn that will pass all arg to all fns and return an Obj with all outputs merged
const mergeOutputs = (...fns) => (...args) => fns.reduce((out, fn) => ({
  ...out,
  ...fn(...args)
}), {})


// takes one arg
const one = (name) => ({ hello: name, world: name })

tincho

const loop = {
  timer: null,
  count: 0,
  start(fn, time=1000, limit = 100) {
    fn(this.stop.bind(this), this.count);
    this.count++;
    if (this.count < limit) {
      this.timer = setTimeout(() => this.start(fn, time, limit), time)
    } else {
      this.stop()

tincho

const shallowCompare = (obj1, obj2) =>
  typeof obj1 === 'object' && typeof obj2 === 'object'
    ? Object.keys(obj1).length === Object.keys(obj2).length &&
      Object.keys(obj1).every(
        key => obj2.hasOwnProperty(key) && obj1[key] === obj2[key]
      )
    : obj1 === obj2

const memoizeByProps = (...props) => Component =>
  React.memo(Component, (prevProps, nextProps) =>

tincho

// iteration 0
// adding deep diving for key paths
// based on getProperty()
// try on tddbin.com

function copyFrom(obj) {
  const values = (...keys) => keys.map(k => getProperty(k)(obj)); 
  return { values };
}

tincho

// make a data uri encoded image from a <video> element using canvas
// (thank you stackoverflow people)
function videoElementToImage(videoElement, width, height) {
    width = width || 360;
    height = height || 240;
    var canvas = document.createElement('canvas');
    canvas.width = width; 
    canvas.height = height;
    var context = canvas.getContext('2d');
    context.drawImage(videoElement, 0, 0, canvas.width, canvas.height);

tincho

function getHeader(url, header) {
	return new Promise(function(resolve, reject) {
		var http = new XMLHttpRequest();
	    	http.open('HEAD', url);
    		http.onreadystatechange = function() {
			if (this.readyState !== this.DONE) return;

			if (this.status != 200) {
				reject(this.status);
			} else {