主讲人
- 月影
- 360前端技术专家
- 奇舞团
-
各司其职
关灯吃面例子：
版本一
light.onclick = function(evt) {
if(light.style.backgroundColor !== 'green'){
document.body.style.backgroundColor = '#000';
document.body.style.color = '#fff';
light.style.backgroundColor = 'green';
}else{
document.body.style.backgroundColor = '';
document.body.style.color = '';
light.style.backgroundColor = '';
}
}
//js直接操作css，违反各司其职原则
lightButton.onclick = function(evt) {
if(main.className === 'light-on'){
main.className = 'light-off';
}else{
main.className = 'light-on';
}
}
//通过修改类名，没有直接操作但是js还是有可能有bug
html,body {
margin: 0;
padding: 0;
width: 100%;
height: 100%;
}
#light {
display: none;
}
#main {
position: relative;
padding: 20px;
width: 100%;
height: 100%;
background-color: #fff;
color: #000;
transition: all .5s;
}
#light:checked + #main {
background-color: #000;
color: #fff;
}
.pic {
float: left;
margin-right: 20px;
}
//通过css实现，但是有兼容性问题
<input id="light" type="checkbox"></input>
<div id="main">
<div class="pic">
<img src="https://p4.ssl.qhimg.com/t01e932bf06236f564f.jpg">
</div>
<div class="content">
<pre>
今天回到家，
煮了点面吃，
一边吃面一边哭，
泪水滴落在碗里，
没有开灯。
</pre>
</div>
<label for="light">
<span id="lightButton"> </span>
<label>
</div>
-
复杂 UI 组件的设计
以轮播图为例介绍UI设计
- 结构设计
<div id="my-slider" class="slider-list">
<ul>
<li class="slider-list__item--selected">
<img src="https://p5.ssl.qhimg.com/t0119c74624763dd070.png"/>
</li>
<li class="slider-list__item">
<img src="https://p4.ssl.qhimg.com/t01adbe3351db853eb3.jpg"/>
</li>
<li class="slider-list__item">
<img src="https://p2.ssl.qhimg.com/t01645cd5ba0c3b60cb.jpg"/>
</li>
<li class="slider-list__item">
<img src="https://p4.ssl.qhimg.com/t01331ac159b58f5478.jpg"/>
</li>
</ul>
</div>
//1. 图片结构是一个列表型结构，所以主体用 <ul>
//2. 使用 css 绝对定位将图片重叠在同一个位置
//3. 轮播图切换的状态使用修饰符（modifier）
//4. 轮播图的切换动画使用 css transition
- API 设计
- getSlectedItem()
- getSlectedItemIndex()
- slidTo()
- slideNext()
- slidePrevious()
class Slider{
constructor(id){
this.container = document.getElementById(id);
this.items = this.container.querySelectorAll('.slider-list__item, .slider-list__item--selected');
}
getSelectedItem(){
const selected = this.container.querySelector('.slider-list__item--selected');
return selected
}
getSelectedItemIndex(){
return Array.from(this.items).indexOf(this.getSelectedItem());
}
slideTo(idx){
const selected = this.getSelectedItem();
if(selected){
selected.className = 'slider-list__item';
}
const item = this.items[idx];
if(item){
item.className = 'slider-list__item--selected';
}
}
slideNext(){
const currentIdx = this.getSelectedItemIndex();
const nextIdx = (currentIdx + 1) % this.items.length;
this.slideTo(nextIdx);
}
slidePrevious(){
const currentIdx = this.getSelectedItemIndex();
const previousIdx = (this.items.length + currentIdx - 1) % this.items.length;
this.slideTo(previousIdx);
}
}
const slider = new Slider('my-slider');
setInterval(() => {
slider.slideNext()
}, 3000)
- 控制流设计
<a class="slide-list__next"></a>
<a class="slide-list__previous"></a>
<div class="slide-list__control">
<span class="slide-list__control-buttons--selected"></span>
<span class="slide-list__control-buttons"></span>
<span class="slide-list__control-buttons"></span>
<span class="slide-list__control-buttons"></span>
</div>
const detail = {index: idx}
const event = new CustomEvent('slide', {bubbles:true, detail})
this.container.dispatchEvent(event)
//用自定义事件进行触发
具体实现
class Slider{
constructor(id, cycle = 3000){
this.container = document.getElementById(id);
this.items = this.container.querySelectorAll('.slider-list__item, .slider-list__item--selected');
this.cycle = cycle;
const controller = this.container.querySelector('.slide-list__control');
if(controller){
const buttons = controller.querySelectorAll('.slide-list__control-buttons, .slide-list__control-buttons--selected');
controller.addEventListener('mouseover', evt=>{
const idx = Array.from(buttons).indexOf(evt.target);
if(idx >= 0){
this.slideTo(idx);
this.stop();
}
});
controller.addEventListener('mouseout', evt=>{
this.start();
});
this.container.addEventListener('slide', evt => {
const idx = evt.detail.index
const selected = controller.querySelector('.slide-list__control-buttons--selected');
if(selected) selected.className = 'slide-list__control-buttons';
buttons[idx].className = 'slide-list__control-buttons--selected';
})
}
const previous = this.container.querySelector('.slide-list__previous');
if(previous){
previous.addEventListener('click', evt => {
this.stop();
this.slidePrevious();
this.start();
evt.preventDefault();
});
}
const next = this.container.querySelector('.slide-list__next');
if(next){
next.addEventListener('click', evt => {
this.stop();
this.slideNext();
this.start();
evt.preventDefault();
});
}
}
getSelectedItem(){
let selected = this.container.querySelector('.slider-list__item--selected');
return selected
}
getSelectedItemIndex(){
return Array.from(this.items).indexOf(this.getSelectedItem());
}
slideTo(idx){
let selected = this.getSelectedItem();
if(selected){
selected.className = 'slider-list__item';
}
let item = this.items[idx];
if(item){
item.className = 'slider-list__item--selected';
}
const detail = {index: idx}
const event = new CustomEvent('slide', {bubbles:true, detail})
this.container.dispatchEvent(event)
slideNext(){
let currentIdx = this.getSelectedItemIndex();
let nextIdx = (currentIdx + 1) % this.items.length;
this.slideTo(nextIdx);
}
slidePrevious(){
let currentIdx = this.getSelectedItemIndex();
let previousIdx = (this.items.length + currentIdx - 1) % this.items.length;
this.slideTo(previousIdx);
}
start(){
this.stop();
this._timer = setInterval(()=>this.slideNext(), this.cycle);
}
stop(){
clearInterval(this._timer);
}
}
const slider = new Slider('my-slider');
slider.start();
优化1.：插件/依赖注入
- 通过plugin注册函数
class Slider{
constructor(id, cycle = 3000){
this.container = document.getElementById(id);
this.items = this.container.querySelectorAll('.slider-list__item, .slider-list__item--selected');
this.cycle = cycle;
}
registerPlugins(...plugins){
plugins.forEach(plugin => plugin(this));
}
getSelectedItem(){
const selected = this.container.querySelector('.slider-list__item--selected');
return selected
}
getSelectedItemIndex(){
return Array.from(this.items).indexOf(this.getSelectedItem());
}
slideTo(idx){
const selected = this.getSelectedItem();
if(selected){
selected.className = 'slider-list__item';
}
const item = this.items[idx];
if(item){
item.className = 'slider-list__item--selected';
}
const detail = {index: idx}
const event = new CustomEvent('slide', {bubbles:true, detail})
this.container.dispatchEvent(event)
}
slideNext(){
const currentIdx = this.getSelectedItemIndex();
const nextIdx = (currentIdx + 1) % this.items.length;
this.slideTo(nextIdx);
}
slidePrevious(){
const currentIdx = this.getSelectedItemIndex();
const previousIdx = (this.items.length + currentIdx - 1) % this.items.length;
this.slideTo(previousIdx);
}
addEventListener(type, handler){
this.container.addEventListener(type, handler)
}
start(){
this.stop();
this._timer = setInterval(()=>this.slideNext(), this.cycle);
}
stop(){
clearInterval(this._timer);
}
}
function pluginController(slider){
const controller = slider.container.querySelector('.slide-list__control');
if(controller){
const buttons = controller.querySelectorAll('.slide-list__control-buttons, .slide-list__control-buttons--selected');
controller.addEventListener('mouseover', evt=>{
const idx = Array.from(buttons).indexOf(evt.target);
if(idx >= 0){
slider.slideTo(idx);
slider.stop();
}
});
controller.addEventListener('mouseout', evt=>{
slider.start();
});
slider.addEventListener('slide', evt => {
const idx = evt.detail.index
const selected = controller.querySelector('.slide-list__control-buttons--selected');
if(selected) selected.className = 'slide-list__control-buttons';
buttons[idx].className = 'slide-list__control-buttons--selected';
});
}
}
function pluginPrevious(slider){
const previous = slider.container.querySelector('.slide-list__previous');
if(previous){
previous.addEventListener('click', evt => {
slider.stop();
slider.slidePrevious();
slider.start();
evt.preventDefault();
});
}
}
function pluginNext(slider){
const next = slider.container.querySelector('.slide-list__next');
if(next){
next.addEventListener('click', evt => {
slider.stop();
slider.slideNext();
slider.start();
evt.preventDefault();
});
}
}
const slider = new Slider('my-slider');
slider.registerPlugins(pluginController, pluginPrevious, pluginNext);
slider.start();
优化2：改进插件
[图片上传失败...(image-37aaae-1586444695444)]
class Slider{
constructor(id, opts = {images:[], cycle: 3000}){
this.container = document.getElementById(id);
this.options = opts;
this.container.innerHTML = this.render();
this.items = this.container.querySelectorAll('.slider-list__item, .slider-list__item--selected');
this.cycle = opts.cycle || 3000;
this.slideTo(0);
}
render(){
const images = this.options.images;
const content = images.map(image => `
<li class="slider-list__item">
<img src="${image}"/>
</li>
`.trim());
return `<ul>${content.join('')}</ul>`;
}
registerPlugins(...plugins){
plugins.forEach(plugin => {
const pluginContainer = document.createElement('div');
pluginContainer.className = '.slider-list__plugin';
pluginContainer.innerHTML = plugin.render(this.options.images);
this.container.appendChild(pluginContainer);
plugin.action(this);
});
}
getSelectedItem(){
const selected = this.container.querySelector('.slider-list__item--selected');
return selected
}
getSelectedItemIndex(){
return Array.from(this.items).indexOf(this.getSelectedItem());
}
slideTo(idx){
const selected = this.getSelectedItem();
if(selected){
selected.className = 'slider-list__item';
}
let item = this.items[idx];
if(item){
item.className = 'slider-list__item--selected';
}
const detail = {index: idx}
const event = new CustomEvent('slide', {bubbles:true, detail})
this.container.dispatchEvent(event)
}
slideNext(){
const currentIdx = this.getSelectedItemIndex();
const nextIdx = (currentIdx + 1) % this.items.length;
this.slideTo(nextIdx);
}
slidePrevious(){
const currentIdx = this.getSelectedItemIndex();
const previousIdx = (this.items.length + currentIdx - 1) % this.items.length;
this.slideTo(previousIdx);
}
addEventListener(type, handler){
this.container.addEventListener(type, handler);
}
start(){
this.stop();
this._timer = setInterval(()=>this.slideNext(), this.cycle);
}
stop(){
clearInterval(this._timer);
}
}
const pluginController = {
render(images){
return `
<div class="slide-list__control">
${images.map((image, i) => `
<span class="slide-list__control-buttons${i===0?'--selected':''}"></span>
`).join('')}
</div>
`.trim();
},
action(slider){
const controller = slider.container.querySelector('.slide-list__control');
if(controller){
const buttons = controller.querySelectorAll('.slide-list__control-buttons, .slide-list__control-buttons--selected');
controller.addEventListener('mouseover', evt => {
const idx = Array.from(buttons).indexOf(evt.target);
if(idx >= 0){
slider.slideTo(idx);
slider.stop();
}
});
controller.addEventListener('mouseout', evt => {
slider.start();
});
slider.addEventListener('slide', evt => {
const idx = evt.detail.index
const selected = controller.querySelector('.slide-list__control-buttons--selected');
if(selected) selected.className = 'slide-list__control-buttons';
buttons[idx].className = 'slide-list__control-buttons--selected';
});
}
}
};
const pluginPrevious = {
render(){
return `<a class="slide-list__previous"></a>`;
},
action(slider){
const previous = slider.container.querySelector('.slide-list__previous');
if(previous){
previous.addEventListener('click', evt => {
slider.stop();
slider.slidePrevious();
slider.start();
evt.preventDefault();
});
}
}
};
const pluginNext = {
render(){
return `<a class="slide-list__next"></a>`;
},
action(slider){
const previous = slider.container.querySelector('.slide-list__next');
if(previous){
previous.addEventListener('click', evt => {
slider.stop();
slider.slideNext();
slider.start();
evt.preventDefault();
});
}
}
};
const slider = new Slider('my-slider', {images: ['https://p5.ssl.qhimg.com/t0119c74624763dd070.png',
'https://p4.ssl.qhimg.com/t01adbe3351db853eb3.jpg',
'https://p2.ssl.qhimg.com/t01645cd5ba0c3b60cb.jpg',
'https://p4.ssl.qhimg.com/t01331ac159b58f5478.jpg'], cycle:3000});
slider.registerPlugins(pluginController, pluginPrevious, pluginNext);
slider.start();
优化3：组件模型抽象
[图片上传失败...(image-b21c0a-1586444695444)]
class Component{
constructor(id, opts = {name, data:[]}){
this.container = document.getElementById(id);
this.options = opts;
this.container.innerHTML = this.render(opts.data);
}
registerPlugins(...plugins){
plugins.forEach(plugin => {
const pluginContainer = document.createElement('div');
pluginContainer.className = `.${name}__plugin`;
pluginContainer.innerHTML = plugin.render(this.options.data);
this.container.appendChild(pluginContainer);
plugin.action(this);
});
}
render(data) {
/* abstract */
return ''
}
}
class Slider extends Component{
constructor(id, opts = {name: 'slider-list', data:[], cycle: 3000}){
super(id, opts);
this.items = this.container.querySelectorAll('.slider-list__item, .slider-list__item--selected');
this.cycle = opts.cycle || 3000;
this.slideTo(0);
}
render(data){
const content = data.map(image => `
<li class="slider-list__item">
<img src="${image}"/>
</li>
`.trim());
return `<ul>${content.join('')}</ul>`;
}
getSelectedItem(){
const selected = this.container.querySelector('.slider-list__item--selected');
return selected
}
getSelectedItemIndex(){
return Array.from(this.items).indexOf(this.getSelectedItem());
}
slideTo(idx){
const selected = this.getSelectedItem();
if(selected){
selected.className = 'slider-list__item';
}
const item = this.items[idx];
if(item){
item.className = 'slider-list__item--selected';
}
const detail = {index: idx}
const event = new CustomEvent('slide', {bubbles:true, detail})
this.container.dispatchEvent(event)
}
slideNext(){
const currentIdx = this.getSelectedItemIndex();
const nextIdx = (currentIdx + 1) % this.items.length;
this.slideTo(nextIdx);
}
slidePrevious(){
const currentIdx = this.getSelectedItemIndex();
const previousIdx = (this.items.length + currentIdx - 1) % this.items.length;
this.slideTo(previousIdx);
}
addEventListener(type, handler){
this.container.addEventListener(type, handler);
}
start(){
this.stop();
this._timer = setInterval(()=>this.slideNext(), this.cycle);
}
stop(){
clearInterval(this._timer);
}
}
const pluginController = {
render(images){
return `
<div class="slide-list__control">
${images.map((image, i) => `
<span class="slide-list__control-buttons${i===0?'--selected':''}"></span>
`).join('')}
</div>
`.trim();
},
action(slider){
let controller = slider.container.querySelector('.slide-list__control');
if(controller){
let buttons = controller.querySelectorAll('.slide-list__control-buttons, .slide-list__control-buttons--selected');
controller.addEventListener('mouseover', evt=>{
var idx = Array.from(buttons).indexOf(evt.target);
if(idx >= 0){
slider.slideTo(idx);
slider.stop();
}
});
controller.addEventListener('mouseout', evt=>{
slider.start();
});
slider.addEventListener('slide', evt => {
const idx = evt.detail.index;
let selected = controller.querySelector('.slide-list__control-buttons--selected');
if(selected) selected.className = 'slide-list__control-buttons';
buttons[idx].className = 'slide-list__control-buttons--selected';
});
}
}
};
const pluginPrevious = {
render(){
return `<a class="slide-list__previous"></a>`;
},
action(slider){
let previous = slider.container.querySelector('.slide-list__previous');
if(previous){
previous.addEventListener('click', evt => {
slider.stop();
slider.slidePrevious();
slider.start();
evt.preventDefault();
});
}
}
};
const pluginNext = {
render(){
return `<a class="slide-list__next"></a>`;
},
action(slider){
let previous = slider.container.querySelector('.slide-list__next');
if(previous){
previous.addEventListener('click', evt => {
slider.stop();
slider.slideNext();
slider.start();
evt.preventDefault();
});
}
}
};
const slider = new Slider('my-slider', {name: 'slide-list', data: ['https://p5.ssl.qhimg.com/t0119c74624763dd070.png',
'https://p4.ssl.qhimg.com/t01adbe3351db853eb3.jpg',
'https://p2.ssl.qhimg.com/t01645cd5ba0c3b60cb.jpg',
'https://p4.ssl.qhimg.com/t01331ac159b58f5478.jpg'], cycle:3000});
slider.registerPlugins(pluginController, pluginPrevious, pluginNext);
slider.start();
-
第三节：局部细节控制
实例一
block.onclick = function(evt){
console.log('hide');
evt.target.className = 'hide';
setTimeout(function(){
document.body.removeChild(block);
}, 2000);
};
执行多次有问题
//如何进行统一的抽象
block.onclick = function(evt){
block.onclick = null;
console.log('hide');
evt.target.className = 'hide';
setTimeout(function(){
document.body.removeChild(block);
}, 2000);
};
//获取异步请求
const api = 'https://test.h5jun.com/index/gaobai?text=';
submitBtn.onclick = async function(evt){
evt.preventDefault();
let {data} = await axios.get(api + t.value);
gaobai.src = 'data:image/jpeg;base64,' + data.data;
console.log('data:image/jpeg;base64,' + data.data)
}
function once(fn){
return function(...args){
if(fn){
let ret = fn.apply(this, args);
fn = null;
return ret;
}
}
}
function foo(idx){
console.log(`I'm called:${idx}`);
}
foo(0);
foo(1);
foo(2);
foo = once(foo);
foo(3);
foo(4);
foo(5);
节流：
function throttle(fn, time = 500){
let timer;
return function(...args){
if(timer == null){
fn.apply(this, args);
timer = setTimeout(() => {
timer = null;
}, time)
}
}
}
btn.onclick = throttle(function(e){
circle.innerHTML = parseInt(circle.innerHTML) + 1;
circle.className = 'fade';
setTimeout(() => circle.className = '', 250);
});
防抖debounce:
function debounce(fn){
let timer = null
return function(...args){
if(timer != null) {
clearTimeout(timer)
}
timer = setTimeout(() => {
fn.apply(this, args)
timer = null
}, 300)
}
}
const api = 'https://test.h5jun.com/index/gaobai?text=';
submitBtn.onclick = debounce(async function(evt){
evt.preventDefault();
let {data} = await axios.get(api + t.value);
gaobai.src = 'data:image/jpeg;base64,' + data.data;
console.log('data:image/jpeg;base64,' + data.data)
})
消费者模式(把数据压缩到一起，再异步执行)
function consumer(fn, time){
let tasks = [],
timer;
return function(...args){
tasks.push(fn.bind(this, ...args));
if(timer == null){
timer = setInterval(() => {
tasks.shift().call(this)
if(tasks.length <= 0){
clearInterval(timer);
timer = null;
}
}, time)
}
}
}
function add(x, y){
let sum = x + y;
console.log(sum);
return sum;
}
let consumerAdd = consumer(add, 1000);
let sum = 0;
for(let i = 0; i < 10; i++){
consumerAdd(sum, i);
}
程序语言里面：
- 指令式，面向过程，面向对象
- 声明式，逻辑的函数式的
js是指令式编程但有函数式特点
reduce方法
function add(x, y){
addMany 通用度不高
function add(x, y){
return x + y;
}
function sub(x, y){
return x - y;
}
function addMany(...args){
return args.reduce(add);
}
function subMany(...args){
return args.reduce(sub);
}
console.log(addMany(1,2,3,4));
console.log(subMany(1,2,3,4));
iterative方法高阶函数 封装其他操作
function iterative(fn){
return function(...args){
return args.reduce(fn.bind(this));
}
}
const add = iterative((x, y) => x + y);
const sub = iterative((x, y) => x - y);
console.log(add(1,2,3,4));
console.log(sub(1,2,3,4));
高阶函数：
自身输入是个函数 或返回函数
点击实例
不通用
例：
switcher.onclick = function(evt){
if(evt.target.className === 'on'){
evt.target.className = 'off';
}else{
evt.target.className = 'on';
}
}
1.提供一个toggl函数
function toggle(...actions){
return function(...args){
let action = actions.shift();
actions.push(action);
return action.apply(this, args);
}
}
switcher.onclick = toggle(
evt => evt.target.className = 'off',
evt => evt.target.className = 'on'
);
方便扩展，直接增加状态就可以
不需要修改逻辑
function toggle(...actions){
return function(...args){
let action = actions.shift();
actions.push(action);
return action.apply(this, args);
}
}
switcher.onclick = toggle(
evt => evt.target.className = 'warn',
evt => evt.target.className = 'off',
evt => evt.target.className = 'on'
);
2.把loop过程抽象出来
function * loop(list, max = Infinity){
let i = 0;
//noprotect
while(i < max){
yield list[i++ % list.length];
}
}
function toggle(...actions){
let action = loop(actions);
return function(...args){
return action.next().value.apply(this, args);
}
}
switcher.onclick = toggle(
evt => evt.target.className = 'warn',
evt => evt.target.className = 'off',
evt => evt.target.className = 'on'
);
总结 :
- 各司其职：JavaScript 尽量只做状态管理
- 结构、API、控制流分离设计 UI 组件
- 插件和模板化，并抽象出组件模型
- 运用过程抽象的技巧来抽象并优化局部 API
