解决实际问题的 24 个 ES6 代码段

const hide = (...el) => [...el].forEach(e => (e.style.display = 'none'));// Examplehide(document.querySelectorAll('img')); // 隐藏页面上的所有 <img> 元素

const hasClass = (el, className) => el.classList.contains(className);// ExamplehasClass(document.querySelector('p.special'), 'special'); // true

const toggleClass = (el, className) => el.classList.toggle(className);// ExampletoggleClass(document.querySelector('p.special'), 'special'); // 该段不再有 'special' 类

const getScrollPosition = (el = window) => ({  x: el.pageXOffset !== undefined ? el.pageXOffset : el.scrollLeft,  y: el.pageYOffset !== undefined ? el.pageYOffset : el.scrollTop});// ExamplegetScrollPosition(); // {x: 0, y: 200}

const scrollToTop = () => {  const c = document.documentElement.scrollTop || document.body.scrollTop;  if (c > 0) {    window.requestAnimationFrame(scrollToTop);    window.scrollTo(0, c - c / 8);  }};// ExamplescrollToTop();

const elementContains = (parent, child) => parent !== child && parent.contains(child);// ExampleselementContains(document.querySelector('head'), document.querySelector('title')); // trueelementContains(document.querySelector('body'), document.querySelector('body')); // false

const elementIsVisibleInViewport = (el, partiallyVisible = false) => {  const { top, left, bottom, right } = el.getBoundingClientRect();  const { innerHeight, innerWidth } = window;  return partiallyVisible    ? ((top > 0 && top < innerHeight) || (bottom > 0 && bottom < innerHeight)) &&        ((left > 0 && left < innerWidth) || (right > 0 && right < innerWidth))    : top >= 0 && left >= 0 && bottom <= innerHeight && right <= innerWidth;};// ExampleselementIsVisibleInViewport(el); // (不完全可见)elementIsVisibleInViewport(el, true); // (部分可见)

const getImages = (el, includeDuplicates = false) => {  const images = [...el.getElementsByTagName('img')].map(img => img.getAttribute('src'));  return includeDuplicates ? images : [...new Set(images)];};// ExamplesgetImages(document, true); // ['image1.jpg', 'image2.png', 'image1.png', '...']getImages(document, false); // ['image1.jpg', 'image2.png', '...']

const detectDeviceType = () =>  /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)    ? 'Mobile'    : 'Desktop';// ExampledetectDeviceType(); // "Mobile" or "Desktop"

const currentURL = () => window.location.href;// ExamplecurrentURL(); // 'https://google.com'

const getURLParameters = url =>  (url.match(/([^?=&]+)(=([^&]*))/g) || []).reduce(    (a, v) => ((a[v.slice(0, v.indexOf('='))] = v.slice(v.indexOf('=') + 1)), a),    {}  );// ExamplesgetURLParameters('http://url.com/page?n=Adam&s=Smith'); // {n: 'Adam', s: 'Smith'}getURLParameters('google.com'); // {}

const formToObject = form =>  Array.from(new FormData(form)).reduce(    (acc, [key, value]) => ({      ...acc,      [key]: value    }),    {}  );// ExampleformToObject(document.querySelector('#form')); // { email: 'test@email.com', name: 'Test Name' }

const get = (from, ...selectors) =>  [...selectors].map(s =>    s      .replace(/\[([^\[\]]*)\]/g, '.$1.')      .split('.')      .filter(t => t !== '')      .reduce((prev, cur) => prev && prev[cur], from)  );const obj = { selector: { to: { val: 'val to select' } }, target: [1, 2, { a: 'test' }] };// Exampleget(obj, 'selector.to.val', 'target[0]', 'target[2].a'); // ['val to select', 1, 'test']

const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);delay(  function(text) {    console.log(text);  },  1000,  'later'); // 一秒后记录 'later' 。

const triggerEvent = (el, eventType, detail) =>  el.dispatchEvent(new CustomEvent(eventType, { detail }));// ExamplestriggerEvent(document.getElementById('myId'), 'click');triggerEvent(document.getElementById('myId'), 'click', { username: 'bob' });

const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts);const fn = () => console.log('!');document.body.addEventListener('click', fn);off(document.body, 'click', fn); // no longer logs '!' upon clicking on the page

const formatDuration = ms => {  if (ms < 0) ms = -ms;  const time = {    day: Math.floor(ms / 86400000),    hour: Math.floor(ms / 3600000) % 24,    minute: Math.floor(ms / 60000) % 60,    second: Math.floor(ms / 1000) % 60,    millisecond: Math.floor(ms) % 1000  };  return Object.entries(time)    .filter(val => val[1] !== 0)    .map(([key, val]) => `${val} ${key}${val !== 1 ? 's' : ''}`)    .join(', ');};// ExamplesformatDuration(1001); // '1 second, 1 millisecond'formatDuration(34325055574); // '397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds'

const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>  (dateFinal - dateInitial) / (1000 * 3600 * 24);// ExamplegetDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 9

const httpGet = (url, callback, err = console.error) => {  const request = new XMLHttpRequest();  request.open('GET', url, true);  request.onload = () => callback(request.responseText);  request.onerror = () => err(request);  request.send();};httpGet(  'https://jsonplaceholder.typicode.com/posts/1',  console.log); // Logs: {"userId": 1, "id": 1, "title": "sample title", "body": "my text"}

const httpPost = (url, data, callback, err = console.error) => {  const request = new XMLHttpRequest();  request.open('POST', url, true);  request.setRequestHeader('Content-type', 'application/json; charset=utf-8');  request.onload = () => callback(request.responseText);  request.onerror = () => err(request);  request.send(data);};const newPost = {  userId: 1,  id: 1337,  title: 'Foo',  body: 'bar bar bar'};const data = JSON.stringify(newPost);httpPost(  'https://jsonplaceholder.typicode.com/posts',  data,  console.log); // Logs: {"userId": 1, "id": 1337, "title": "Foo", "body": "bar bar bar"}

const counter = (selector, start, end, step = 1, duration = 2000) => {  let current = start,    _step = (end - start) * step < 0 ? -step : step,    timer = setInterval(() => {      current += _step;      document.querySelector(selector).innerHTML = current;      if (current >= end) document.querySelector(selector).innerHTML = end;      if (current >= end) clearInterval(timer);    }, Math.abs(Math.floor(duration / (end - start))));  return timer;};// Examplecounter('#my-id', 1, 1000, 5, 2000); // 为 id="my-id" 的元素创建一个两秒的计时器

const copyToClipboard = str => {  const el = document.createElement('textarea');  el.value = str;  el.setAttribute('readonly', '');  el.style.position = 'absolute';  el.style.left = '-9999px';  document.body.appendChild(el);  const selected =    document.getSelection().rangeCount > 0 ? document.getSelection().getRangeAt(0) : false;  el.select();  document.execCommand('copy');  document.body.removeChild(el);  if (selected) {    document.getSelection().removeAllRanges();    document.getSelection().addRange(selected);  }};// ExamplecopyToClipboard('Lorem ipsum'); // 'Lorem ipsum' copied to clipboard.

const isBrowserTabFocused = () => !document.hidden;// ExampleisBrowserTabFocused(); // true

const fs = require('fs');const createDirIfNotExists = dir => (!fs.existsSync(dir) ? fs.mkdirSync(dir) : undefined);// ExamplecreateDirIfNotExists('test'); // creates the directory 'test', if it doesn't exist