24个解决实际问题的ES6代码段

1、如何隐藏所有指定元素？

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

2、 如何确认元素是否具有指定的类？

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

3、 如何切换元素的类？

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

4、如何获取当前页面的滚动位置？

 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、如何平滑滚动到页面顶部？

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、 如何确认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、如何确认指定元素是否在视口可见？

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); // (不完全可见)      elementIsVisibleInViewport(el, true); // (部分可见)

8、如何获取一个元素内的所有图像？

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

9、如何分辨设备是移动设备还是桌面设备？

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

10、 如何获取当前 URL？

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

11、 如何创建一个包含当前 URL 参数的对象？

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、如何将一组表单元素编码为一个对象？

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、 如何从对象中检索给定选择器指示的一组属性？

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、 如何在等待一定时间后调用提供的函数（单位毫秒）？

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

15、如何在给定元素上触发特定事件，且可选传递自定义数据？

 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、 如何移除一个元素的事件侦听器？

 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、 如何获得给定毫秒数的可读格式？

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、 如何获取两个日期之间的天数间隔？

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

19、 如何对传递的 URL 进行 GET 请求？

 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、 如何对传递的 URL 进行 POST 请求？

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、 如何为指定选择器创建具有指定范围、步长和持续时间的计时器？

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); // 为 id="my-id" 的元素创建一个两秒的计时器

22、 如何将一个字符串复制到剪贴板？

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、 如何确定页面的浏览器选项卡是否处于前台活跃状态？

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

24、如果一个目录不存在，如何创建它？

 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