24个解决实际问题的ES6代码片段(小结)

const getScrollPosition = (el = window) => ({
 x: el.pageXOffset !== undefined "htmlcode">

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

// Example
scrollToTop();




递归的方法不断调用使用scrollToTop()，requestAnimationFrame方法告诉浏览器——你希望执行一个动画，并且要求浏览器在下次重绘之前调用指定的回调函数更新动画。它的回调函数执行次数通常与浏览器屏幕刷新次数相匹配，所以效果会比较平滑。
获取当前页面滚动条纵坐标的位置：document.body.scrollTop与document.documentElement.scrollTop
获取当前页面滚动条横坐标的位置：document.body.scrollLeft与document.documentElement.scrollLeft
6.如何检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.如何检查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
 "htmlcode">

const getImages = (el, includeDuplicates = false) => {
 const images = [...el.getElementsByTagName('img')].map(img => img.getAttribute('src'));
 return includeDuplicates "htmlcode">

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




10.如何获取当前URL




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

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




11.如何创建包含当前URL参数的对象？




const getURLParameters = url =>
 (url.match(/([^"htmlcode">

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' }




Array.from方法用于将两类对象转为真正的数组。类似数组的对象（array-like object）和可遍历（iterable）的对象（包括 ES6 新增的数据结构 Set 和 Map）。

reducer 函数接收4个参数:

  
Accumulator (acc) (累计器)
  
Current Value (cur) (当前值)
  
Current Index (idx) (当前索引)
  
Source Array (src) (源数组)

13.如何从对象中检索出给定的一组属性？




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.延迟调用提供的函数（以毫秒为单位）




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

// Logs 'later' after one second.




15.如何在给定元素上触发特定事件，并可选地传递自定义数据？




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

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




构造方法 CustomerEvent() 创建一个新的 CustomEvent 对象。

CustomEvent 事件是由程序创建的，可以有任意自定义功能的事件。
16.如何从元素中移除事件侦听器？




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.将给定的毫秒数转换为可读格式




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 "htmlcode">

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发出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发出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. 如何为指定的选择器创建具有指定范围、步骤和持续时间的计数器？




const counter = (selector, start, end, step = 1, duration = 2000) => {
 let current = start,
 _step = (end - start) * step < 0 "my-id"




22.如何将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 "htmlcode">

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

// Example
isBrowserTabFocused(); // true




24.如果不存在目录，则如何创建




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

// Example
createDirIfNotExists('test'); // creates the directory




以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。

            
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