1.怎样隐蔽全部指定的元素
const hide = (el) => Array.from(el).forEach(e => (e.style.display = 'none'));// 事例: 隐蔽页面上全部`<p>`元素hide(document.querySelectorALL('p'))2.怎样查抄元素是否具有指定的类？
页面DOM内里的每个节点上都有一个 $\color{#FF0000}{classList}$对象，程序员可以利用内里的方法新增、删除、修改、查询节点上的class类。
const hasClass = (el, className) => el.classList.contains(className)// 事例hasClass(document.querySelector('p.special'), 'spec') // true3.怎样切换一个元素的类?
const toggleClass = (el, className) => el.classList.toggle(className)// 事例 移除 p 具有类`special`的 speci 类toggleClass(document.querySelector('p.special'), 'speci')4.怎样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});// 事例getScrollPosition(); // {x: 0, y: 200}5.怎样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); }}// 事例scrollToTop()$\color{#FF0000}{window.requestAnimationFrame()}$ 告诉欣赏器——你渴望实行一个动画，而且要求欣赏器在下次重绘之前调用指定的回调函数更新动画。该方法须要传入一个回调函数作为参数，该回调函数会在欣赏器下一次重绘之前实行。
$\color{#FF0000}{requestAnimationFrame:}$
上风：由体系决定回调函数的实行机会。60Hz的革新频率，那么每次革新的隔断中会实行一次回调函数，不会引起丢帧，不会卡顿。
6.怎样查抄父元素是否包罗子元素？
const elementContains = (parent, child) => parent !== child && parent.contains(child);// 事例elementContains(document.querySelector('head'), document.querySelector('title')); // trueelementContains(document.querySelector('body'), document.querySelector('body')); // false7.怎样查抄指定的元素在视口中是否可见？
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;};// 事例elementIsVisibleInViewport(el); // 须要左右可见elementIsVisibleInViewport(el, true); // 须要全屏(上下左右)可以见8.怎样获取元素中的全部图像？
const getImages = (el, includeDuplicates = false) => { const images = [...el.getElementsByTagName('img')].map(img => img.getAttribute('src')); return includeDuplicates ? images : [...new Set(images)];};// 事例：includeDuplicates 为 true 表现须要清除重复元素getImages(document, true); // ['image1.jpg', 'image2.png', 'image1.png', '...']getImages(document, false); // ['image1.jpg', 'image2.png', '...']9.怎样确定装备是移动装备照旧台式机/条记本电脑？
const detectDeviceType = () => /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ? 'Mobile' : 'Desktop';// 事例detectDeviceType(); // "Mobile" 移动装备 or "Desktop" 台式机10.怎样创建一个包罗当前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), {} );// 事例getURLParameters('http://url.com/page?n=Adam&s=Smith'); // {n: 'Adam', s: 'Smith'}getURLParameters('google.com'); // {}11.怎样将一组表单元素转化为对象？
const formToObject = form => Array.from(new FormData(form)).reduce( (acc, [key, value]) => ({ ...acc, [key]: value }), {} );// 事例formToObject(document.querySelector('#form')); // { email: 'test@email.com', name: 'Test Name' }12.怎样从对象检索给定选择器指示的一组属性？
const get = (from, ...selectors) => [...selectors].map(s => s .replace(/\[([^\[\]]*)\]/g, '.$1.') .split('.') .filter(t => t !== '') .reduce((prev, cur) => prev && prev[cur], from) );const obj = { selector: { to: { val: 'val to select' } }, target: [1, 2, { a: 'test' }] };// Exampleget(obj, 'selector.to.val', 'target[0]', 'target[2].a'); // ['val to select', 1, 'test']13.怎样在等待指定时间后调用提供的函数？
const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);delay( function(text) { console.log(text); }, 1000, 'later'); // 1秒后打印 'later'14.怎样在给定元素上触发特定变乱且能选择地转达自界说数据？
const triggerEvent = (el, eventType, detail) => el.dispatchEvent(new CustomEvent(eventType, { detail }));// 事例triggerEvent(document.getElementById('myId'), 'click');triggerEvent(document.getElementById('myId'), 'click', { username: 'bob' });自界说变乱的函数有$\color{#FF0000}{Event}$ 、$\color{#FF0000}{CustomEvent}$ 和 $\color{#FF0000}{dispatchEvent}$
// 向 window派发一个resize内置变乱window.dispatchEvent(new Event('resize')) // 直接自界说变乱，利用 Event 构造函数：var event = new Event('build');var elem = document.querySelector('#id')// 监听变乱elem.addEventListener('build', function (e) { ... }, false);// 触发变乱.elem.dispatchEvent(event);$\color{#FF0000}{CustomEvent}$ 可以创建一个更高度自界说变乱，还可以附带一些数据，具体用法如下：
var myEvent = new CustomEvent(eventname, options);此中 options 可以是：{ detail: { ... }, bubbles: true, //是否冒泡 cancelable: false //是否取消默认变乱}此中 $\color{#FF0000}{detail}$ 可以存放一些初始化的信息，可以在触发的时间调用。其他属性就是界说该变乱是否具有冒泡等等功能。
内置的变乱会由欣赏器根据某些操作举行触发，自界说的变乱就须要人工触发。 $\color{#FF0000}{dispatchEvent}$ 函数就是用来触发某个变乱：
element.dispatchEvent(customEvent);上面代码表现，在 $\color{#FF0000}{element}$ 上面触发 $\color{#FF0000}{customEvent}$ 这个变乱。
// add an appropriate event listenerobj.addEventListener("cat", function(e) { process(e.detail) }); // create and dispatch the eventvar event = new CustomEvent("cat", {"detail":{"hazcheeseburger":true}});obj.dispatchEvent(event);利用自界说变乱须要注意兼容性问题，而利用 jQuery 就简单多了：// 绑定自界说变乱$(element).on('myCustomEvent', function(){}); // 触发变乱$(element).trigger('myCustomEvent');// 别的，你还可以在触发自界说变乱时转达更多参数信息： $( "p" ).on( "myCustomEvent", function( event, myName ) { $( this ).text( myName + ", hi there!" );});$( "button" ).click(function () { $( "p" ).trigger( "myCustomEvent", [ "John" ] );});15.怎样从元素中移除变乱监听器?
const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts);const fn = () => console.log('!');document.body.addEventListener('click', fn);off(document.body, 'click', fn); 16.怎样得到给定毫秒数的可读格式？
const formatDuration = ms => { if (ms < 0) ms = -ms; const time = { day: Math.floor(ms / 86400000), hour: Math.floor(ms / 3600000) % 24, minute: Math.floor(ms / 60000) % 60, second: Math.floor(ms / 1000) % 60, millisecond: Math.floor(ms) % 1000 }; return Object.entries(time) .filter(val => val[1] !== 0) .map(([key, val]) => `${val} ${key}${val !== 1 ? 's' : ''}`) .join(', ');};// 事例formatDuration(1001); // '1 second, 1 millisecond'formatDuration(34325055574); // '397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds'17.怎样得到两个日期之间的差别（以天为单元）？
const getDaysDiffBetweenDates = (dateInitial, dateFinal) => (dateFinal - dateInitial) / (1000 * 3600 * 24);// 事例getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 918.怎样向转达的URL发出GET哀求
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); // {"userId": 1, "id": 1, "title": "sample title", "body": "my text"}19.怎样对转达的URL发出POST哀求
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); // {"userId": 1, "id": 1337, "title": "Foo", "body": "bar bar bar"}20.怎样为指定选择器创建具有指定范围，步长和连续时间的计数器？
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;};// 事例counter('#my-id', 1, 1000, 5, 2000); // 让 `id=“my-id”`的元素创建一个2秒计时器21.怎样将字符串复制到剪贴板？
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); }};// 事例copyToClipboard('Lorem ipsum'); // 'Lorem ipsum' copied to clipboard |
