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24 個解決JavaScript實際問題的 ES6 代碼片段

24 個解決JavaScript實際問題的 ES6 代碼片段

英文 | https://dev.to/madza/20-modern-es6-snippets-to-solve-practical-js-problems-3n83

翻譯 | 楊小愛

我從 30 seconds of code 網站中挑選了一些我認為有用的短代碼片段，這是一個很棒的學習資源，有興趣的話，可以多上去看看。

在今天的内容中，我嘗試根據它們的實際用途對它們進行排序，解決我們在項目中可能遇到的常見問題：

1、隐藏指定的所有元素

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


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

2、檢查元素是否有指定的類

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


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

3、如何切換元素的類

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、如何擷取目前頁面的滾動位置

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、如何平滑滾動到頁面頂部

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、如何檢查父元素是否包含子元素

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、如何檢查指定的元素在視口中是否可見

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、如何擷取元素内的所有圖像

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、如何判斷裝置是移動裝置還是桌上型電腦/筆記本電腦

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


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

10、如何擷取目前網址

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


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

11、如何建立一個包含目前URL參數的對象

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、如何将一組表單元素編碼為一個對象

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


// Example
formToObject(document.querySelector('#form')); // { email: '[email protected]', name: 'Test Name' }

13、如何從對象中檢索給定選擇器訓示的一組屬性

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、wait（毫秒）後如何調用提供的函數

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


// Logs 'later' after one second.

15、如何在給定元素上觸發特定事件，可選擇傳遞自定義資料

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、如何從元素中移除事件監聽器

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、如何擷取給定毫秒數的可讀格式

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、如何獲得兩個日期之間的差異（以天為機關）

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


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

19、如何向傳遞的URL發起GET請求

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、如何向傳遞的URL發起POST請求

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、如何為指定的選擇器建立一個指定範圍、步長和持續時間的計數器

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、如何将字元串複制到剪貼闆

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、如何判斷頁面的浏覽器标簽是否有焦點

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


// Example
isBrowserTabFocused(); // true

24、如果目錄不存在，如何建立

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

寫在最後

以上就是我在工作與學習中收集整理下來的24個代碼片段，對我來講，還是非常有用的，是以，我将它分享出來，也希望對您有所幫助。

最後，感謝您的閱讀，如果您覺得非常有用，請記得點贊我，關注我，同時，您也可以将它分享給您身邊做開發的朋友，非常感謝。

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