24个解决实际问题的ES6代码片段
30 seconds of code 中文版翻译。收集有用的 Javascript 片段, 你可以在30秒或更少的时间里理解。
https://github.com/kujian/30-seconds-of-code#table-of-contents
- 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
- 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
- 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
- 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}
- 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();
- 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
- 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)
- 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', '...']
- 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"
- 如何获取当前 URL？
const currentURL = () => window.location.href; // Example currentURL(); // 'https://google.com'
- 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'); // {}
- 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' }
- 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, '.$1.') .split('.') .filter(t => t !== '') .reduce((prev, cur) => prev && prev[cur], from) ); const obj = { selector: { to: { val: 'val to select' } }, target: [1, 2, { a: 'test' }] }; // Example get(obj, 'selector.to.val', 'target[0]', 'target[2].a'); // ['val to select', 1, 'test']
- 如何在等待一定时间后调用提供的函数（单位毫秒）？
const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args); delay( function(text) { console.log(text); }, 1000, 'later' ); // 一秒后记录 'later'
- 如何在给定元素上触发特定事件，且可选传递自定义数据？
const triggerEvent = (el, eventType, detail) => el.dispatchEvent(new CustomEvent(eventType, { detail })); // Examples triggerEvent(document.getElementById('myId'), 'click'); triggerEvent(document.getElementById('myId'), 'click', { username: 'bob' });
- 如何移除一个元素的事件侦听器？
const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts); const fn = () => console.log('!'); document.body.addEventListener('click', fn); off(document.body, 'click', fn); // no longer logs '!' upon clicking on the page
- 如何获得给定毫秒数的可读格式？
const formatDuration = ms => { if (ms < 0) ms = -ms; const time = { day: Math.floor(ms / 86400000), hour: Math.floor(ms / 3600000) % 24, minute: Math.floor(ms / 60000) % 60, second: Math.floor(ms / 1000) % 60, millisecond: Math.floor(ms) % 1000 }; return Object.entries(time) .filter(val => val[1] !== 0) .map(([key, val]) => `${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'
- 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
- 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"}
- 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"}
- 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
- 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.
- 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
- 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
