Video học lập trình mỗi ngày

ES6 giờ đây đã được những developer javascript sử dụng chúng thường xuyên trong lập trình js. Và trong bài viết này thì anonystick sẽ giới thiệu cho các bạn về 24 đoạn mã được sử dụng thường xuyên và thực tế nhất của tác giả Madza.

Tôi tự tay chọn một số code hữu ích nhất tron 30 seconds of code. Đó là một nguồn tài nguyên tuyệt vời cho những bạn muốn phát triển còn đường dựa trên ngôn ngữ javascript. Ở trong đó có rất nhiều điều tuyệt vời có thể tôi đã bỏ sót. Trong bài viết này, tôi đã cố gắng sắp xếp chúng dựa trên việc sử dụng thực tế của chúng, và tôi có thể chắc chắn bạn cũng đã tìm kiếm những điều tượng tự cho dự án của mình.

1.How to hide all elements specified?

const hide = (...el) => [...el].forEach(e => (e.style.display = 'none'));

// Example
hide(document.querySelectorAll('img')); // Hides all  elements on the page

2.How to check if the element has the specified class?

const hasClass = (el, className) => el.classList.contains(className);

// Example
hasClass(document.querySelector('p.special'), 'special'); // true

3.How to toggle a class for an element?

const toggleClass = (el, className) => el.classList.toggle(className);

// Example
toggleClass(document.querySelector('p.special'), 'special'); 
// The paragraph will not have the 'special' class anymore

4.How to get the scroll position of the current page?

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

// Example
getScrollPosition(); // {x: 0, y: 200}

5.How to smooth-scroll to the top of the page?

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

// Example
scrollToTop();

6.How to check if the parent element contains the child element?

const elementContains = (parent, child) => parent !== child && parent.contains(child);

// Examples
elementContains(document.querySelector('head'), document.querySelector('title')); 
// true
elementContains(document.querySelector('body'), document.querySelector('body')); // false

7.How to check if the element specified is visible in the viewport?

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;
};

// Examples
elementIsVisibleInViewport(el); // (not fully visible)
elementIsVisibleInViewport(el, true); // (partially visible)

8.How to fetch all images within an element?

const getImages = (el, includeDuplicates = false) => {
  const images = [...el.getElementsByTagName('img')].map(img => img.getAttribute('src'));
  return includeDuplicates ? images : [...new Set(images)];
};

// Examples
getImages(document, true); // ['image1.jpg', 'image2.png', 'image1.png', '...']
getImages(document, false); // ['image1.jpg', 'image2.png', '...']

9.How to figure out if the device is a mobile device or a desktop/laptop?

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

// Example
detectDeviceType(); // "Mobile" or "Desktop"

10.How to get the current URL?

const currentURL = () => window.location.href;

// Example
currentURL(); // 'https://google.com'

11.How to create an object containing the parameters of the current URL?

const getURLParameters = url =>
  (url.match(/([^?=&]+)(=([^&]*))/g) || []).reduce(
    (a, v) => ((a[v.slice(0, v.indexOf('='))] = v.slice(v.indexOf('=') + 1)), a),
    {}
  );

// Examples
getURLParameters('http://url.com/page?n=Adam&s=Smith'); // {n: 'Adam', s: 'Smith'}
getURLParameters('google.com'); // {}

12.How to encode a set of form elements as an object?

const formToObject = form =>
  Array.from(new FormData(form)).reduce(
    (acc, [key, value]) => ({
      ...acc,
      [key]: value
    }),
    {}
  );

// Example
formToObject(document.querySelector('#form')); // { email: 'test@email.com', name: 'Test Name' }

13.How to retrieve a set of properties indicated by the given selectors from an object?

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' }] };

// Example
get(obj, 'selector.to.val', 'target[0]', 'target[2].a'); // ['val to select', 1, 'test']

14.How to invoke the provided function after wait (in milliseconds)?

const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);
delay(
  function(text) {
    console.log(text);
  },
  1000,
  'later'
); 

// Logs 'later' after one second.

15.How to trigger a specific event on a given element, optionally passing custom data?

const triggerEvent = (el, eventType, detail) =>
  el.dispatchEvent(new CustomEvent(eventType, { detail }));

// Examples
triggerEvent(document.getElementById('myId'), 'click');
triggerEvent(document.getElementById('myId'), 'click', { username: 'bob' });

16.How to remove an event listener from an element?

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

17.How to get readable format of the given number of milliseconds?

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(', ');
};

// Examples
formatDuration(1001); // '1 second, 1 millisecond'
formatDuration(34325055574); // '397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds'

18.How to get the difference (in days) between two dates?

const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>
  (dateFinal - dateInitial) / (1000 * 3600 * 24);

// Example
getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 9

19.How to make a GET request to the passed URL?

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"}

20.How to make a POST request to the passed URL?

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"}

21.How to create a counter with the specified range, step and duration for the specified selector?

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;
};

// Example
counter('#my-id', 1, 1000, 5, 2000); // Creates a 2-second timer for the element with id="my-id"

22.How to copy a string to the clipboard?

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);
  }
};

// Example
copyToClipboard('Lorem ipsum'); // 'Lorem ipsum' copied to clipboard.

23.How to find out if the browser tab of the page is focused?

const isBrowserTabFocused = () => !document.hidden;

// Example
isBrowserTabFocused(); // true

24.How to create a directory, if it does not exist?

const fs = require('fs');
const createDirIfNotExists = dir => (!fs.existsSync(dir) ? fs.mkdirSync(dir) : undefined);

// Example
createDirIfNotExists('test'); // creates the directory 'test', if it doesn't exist

Source: https://dev.to/madarsbiss/20-modern-es6-snippets-to-solve-practical-js-problems-3n83