进入目录安装依赖:
npm i 或者 yarn install
开发：
npm run dev
npm install 太慢，试试yarn吧。建议用npm install yarn -g进行安装。
五、Generator函数的概念
Generator 函数是协程在 ES6 的实现，最大特点就是可以交出函数的执行权（即暂停执行）。
function* gen(x){
var y = yield x + 2;
return y;
}
上面代码就是一个 Generator 函数。它不同于普通函数，是可以暂停执行的，所以函数名之前要加星号，以示区别。
整个 Generator 函数就是一个封装的异步任务，或者说是异步任务的容器。异步操作需要暂停的地方，都用 yield 语句注明。Generator 函数的执行方法如下。
var g = gen(1);
g.next() // { value: 3, done: false }
g.next() // { value: undefined, done: true }
上面代码中，调用 Generator 函数，会返回一个内部指针（即遍历器 ）g 。这是 Generator 函数不同于普通函数的另一个地方，即执行它不会返回结果，返回的是指针对象。调用指针 g 的 next 方法，会移动内部指针（即执行异步任务的第一段），指向第一个遇到的 yield 语句，上例是执行到 x + 2 为止。
换言之，next 方法的作用是分阶段执行 Generator 函数。每次调用 next 方法，会返回一个对象，表示当前阶段的信息（ value 属性和 done 属性）。value 属性是 yield 语句后面表达式的值，表示当前阶段的值；done 属性是一个布尔值，表示 Generator 函数是否执行完毕，即是否还有下一个阶段。
http://www.ruanyifeng.com/blog/2015/04/generator.html
变量声明
const 和 let
不要用 var，而是用 const 和 let，分别表示常量和变量。不同于 var 的函数作用域，const 和 let 都是块级作用域。
const DELAY = 1000;
let count = 0; count = count + 1;
箭头函数
函数的快捷写法，不需要通过 function 关键字创建函数，并且还可以省略 return 关键字。
同时，箭头函数还会继承当前上下文的 this 关键字。
比如：
[1, 2, 3].map(x => x + 1); // [2, 3, 4]
等同于：
[1, 2, 3].map((function(x) { return x + 1; }).bind(this));
模块的 Import 和 Export
import 用于引入模块，export 用于导出模块。
比如：
// 引入全部
import dva from 'dva'; // 引入部分 import { connect } from 'dva'; import { Link, Route } from 'dva/router'; // 引入全部并作为 github 对象 import * as github from './services/github'; // 导出默认 export default App; // 部分导出，需 import { App } from './file'; 引入 export class App extend Component {};
对象字面量改进
这是析构的反向操作，用于重新组织一个 Object 。
const name = 'duoduo'; const age = 8; const user = { name, age }; // { name: 'duoduo', age: 8 }
定义对象方法时，还可以省去 function 关键字。
app.model({
reducers: {
add() {} // 等同于 add: function() {} }, effects: { *addRemote() {} // 等同于 addRemote: function*() {} }, });
Spread Operator
Spread Operator 即 3 个点 ...，有几种不同的使用方法。
可用于组装数组。
const todos = ['Learn dva']; [...todos, 'Learn antd']; // ['Learn dva', 'Learn antd']
也可用于获取数组的部分项。
const arr = ['a', 'b', 'c']; const [first, ...rest] = arr; rest; // ['b', 'c'] // With ignore const [first, , ...rest] = arr; rest; // ['c']
还可收集函数参数为数组。
function directions(first, ...rest) {
console.log(rest); } directions('a', 'b', 'c'); // ['b', 'c'];
代替 apply。
function foo(x, y, z) {}
const args = [1,2,3]; // 下面两句效果相同 foo.apply(null, args); foo(...args);
区分 apply和call就一句话： foo.call(this,arg1,arg2,arg3)==foo.apply(thsi,arguments)==this.foo(arg1,arg2,arg3); 两者区别 call 和 apply都属于Function.prototype的一个方法，它是Javascript引擎内在实现的，
因为属于Function.prototype对象的实例，也就是每个方法都有call,apply属性，这两个方法很容易混淆，
因为他们的作用一样，只是使用方式不同（传递的参数不同）。
不同点分析
我们针对上面的foo.call(this,arg1,arg2,arg3)展开分析：<br/>
foo 是一个方法，this是方法执行时上下文相关对象，永远指向当前代码所处在的对象中。arg1,arg2,arg3是传给foo方法的参数。
function A(){
var message="a";
return{
getMessage:function(){return this.message}
}
}
function B(){
var message="b";
return{
setMessage:function(message){this.message=message}
}
}
var a=new A();
var b=new B();
b.setMessage.call(a,"a的消息");
alert(a.getMessage()); //这里将输出“a的消息”
这就是动态语言Javascript call的威力所在，简直是无中生有，对象的方法可以任意指派，而对象本身是没有这个方法的。注意，指派通俗地讲就是把方法借给另一个对象调用，原理上时方法执行时上下文的对象改变了。
所以，b.setMessage.call(a,"a 的消息");就等于用a做执行时上下文对象调用b对象的setMessage()方法，而这个过程与b一点关系都没有。作用等效于a.setMessage()
下面说一下apply的使用场景
function print(a,b,c,d){
console.log(a+b+c+d);
}
function example(a,b,c,d){
//用call方式借用print，参数显式打散传递
print.call(this,a,b,c,d);
//apply方式借用print，参数作为一个数组传递
print.apply(this,arguments);
//或者这样写
print.apply(this,[a,b,c,d]);
}
example('我','不','开','心');
从上面的例子我们发现，call和apply方法除了第一个参数相同，call方法的其他参数一次传递给借用的方法做参数，而apply就两个参数，第二个参数是借用方法的参数组成的数组。
总结一下，当参数明确时可用call，当参数不明确时用apply并结合arguments
https://github.com/Jafeney/myBlog/blob/master/JavaScript%E6%A0%B8%E5%BF%83%E2%80%94%E2%80%94call%E5%92%8Capply%E7%9A%84%E5%8C%BA%E5%88%AB.md
对于 Object 而言，用于组合成新的 Object 。(ES2017 stage-2 proposal)
const foo = {
a: 1,
b: 2, }; const bar = { b: 3, c: 2, }; const d = 4; const ret = { ...foo, ...bar, d }; // { a:1, b:3, c:2, d:4 }
此外，在 JSX 中 Spread Operator 还可用于扩展 props，详见 Spread Attributes。
定义全局 CSS
CSS Modules 默认是局部作用域的，想要声明一个全局规则，可用 :global 语法。
比如：
.title {
color: red;
}
:global(.title) {
color: green;
}
然后在引用的时候：
<App className={styles.title} /> // red
<App className="title" /> // green
classnames Package
在一些复杂的场景中，一个元素可能对应多个 className，而每个 className 又基于一些条件来决定是否出现。这时，classnames 这个库就非常有用。
import classnames from 'classnames';
const App = (props) => {
const cls = classnames({
btn: true,
btnLarge: props.type === 'submit',
btnSmall: props.type === 'edit',
});
return <div className={ cls } />;
}
这样，传入不同的 type 给 App 组件，就会返回不同的 className 组合：
<App type="submit" /> // btn btnLarge
<App type="edit" /> // btn btnSmall
https://github.com/dvajs/dva-knowledgemap
结构划分
很多同学在搭建项目的时候，往往忽略项目结构的划分，实际上合理的项目划分往往能够提供规范的项目搭建思路。 在 dva 架构的项目中，我们推荐的目录基本结构为：
.
├── /mock/ # 数据mock的接口文件
├── /src/ # 项目源码目录
│ ├── /components/ # 项目组件 │ ├── /routes/ # 路由组件（页面维度） │ ├── /models/ # 数据模型 │ ├── /services/ # 数据接口 │ ├── /utils/ # 工具函数 │ ├── route.js # 路由配置 │ ├── index.js # 入口文件 │ ├── index.less │ └── index.html ├── package.json # 项目信息 └── proxy.config.js # 数据mock配置
大家可以发现，dva 将项目中所有可能出现的功能性都映射到了对应的目录当中，并且对整个项目的功能从目录上也有了清晰的体现，所以我们建议你的项目也按照这个目录来组织文件，如果你是用的是 dva-cli 工具生成的 dva 的脚手架模板，那么会帮你按照这样目录生成好。
https://github.com/dvajs/dva-docs/blob/master/v1/zh-cn/tutorial/02-%E5%88%92%E5%88%86%E7%BB%93%E6%9E%84.md
Getting Started
This article will lead you to create dva app quickly, and learn all new concepts.
Final App.
This app is used to test click speed, by collecting click count within 1 second.
Some questions you may ask.
- How to create app?
- How to organize code after created app?
- How to build, deploy and publish after development?
And somethings about code organization.
- How to write Component?
- How to write CSS?
- How to write Model?
- How to connect Model and Component?
- How to update State after user interaction?
- How to handle async logic?
- How to config router?
And.
- If I want to use localStorage to save Highest Record, what to do?
- If we want to support keyboard click rate test, what to do?
We can takes these questions to read this article. But don't worry, all the code we need is about 70 lines.
Install dva-cli
dva-cli is the cli tool for dva, include init, new.
$ npm install -g dva-cli
After installed, you can check version with dva -v, and view help info with dva -h.
Create new App
After installed dva-cli, we can create a new app with it, called myapp.
$ dva new myapp --demo
Notice: --demo option is only used for creating demo level app. If you want to create normal project, don't add this option.
cd myapp, and start it.
$ cd myapp
$ npm start
After a few seconds, you will get these outputs:
proxy: listened on 8989
livereload: listening on 35729
173/173 build modules
webpack: bundle build is now finished.
(Press Ctrl-C if you want to close server)
Open http://localhost:8989/ in browser. If success, you will see a page with "Hello Dva".
Define models
When get the task, you should not write code immediately. But recommend to do state design in god mode.
- design models
- design components
- connect models and components
With this task, we define model in this:
app.model({
namespace: 'count', state: { record : 0, current: 0, }, });
namespace is the key where model state is in global state. state is the default data for model. Then record presents highest record，and current presents current click speed.
Write components
After designed model, we start to write component. Recommend to organize Component with stateless functions. Because we don't need state almost in dva architecture.
import styles from './index.less'; const CountApp = ({count, dispatch}) => { return ( <div className={styles.normal}> <div className={styles.record}>Highest Record: {count.record}</div> <div className={styles.current}>{count.current}</div> <div className={styles.button}> <button onClick={() => { dispatch({type: 'count/add'}); }}>+</button> </div> </div> ); };
Notice:
-
import styles from './index.less';, and then usestyles.xxxto define css classname is the solution of css-modules - passes in two props，
countanddispatch.countis the state in model, bind with connect. Anddispatchis used to trigger an action -
dispatch({type: 'count/add'})means trigger an action{type: 'count/add'}. View Actions@redux.js.org on what's an action.
Update state
reducer is the only one which can update state, this make our app stable, all data modification is traceable. reducer is pure function, accept arguments state and action, return new state.
(state, action) => newState
We need two reducers, add and minus. Please notice add will only be recorded if it's highest.
Notice:
addandminusdon't need to add namespace prefix incountmodel. But if outside the model, action must prefix namespace separated with/. e.g.count/add.
app.model({
namespace: 'count',
state: {
record: 0,
current: 0,
},
+ reducers: {
+ add(state) {
+ const newCurrent = state.current + 1; + return { ...state, + record: newCurrent > state.record ? newCurrent : state.record, + current: newCurrent, + }; + }, + minus(state) { + return { ...state, current: state.current - 1}; + }, + }, });
Notice:
- Confused with
...operator? It's used for extend Object, similar toObject.extend -
add(state) {}is equal toadd: function(state) {}
Bind Data
Remember
countanddispatchprops used in the Component before? Where are them come from?
After define Model and Component, we need to connect them together. After connect, Component can use the data from Model, and Model can receive actions dispatched from Component.
In this task, we only need to bind count .
function mapStateToProps(state) {
return { count: state.count }; } const HomePage = connect(mapStateToProps)(CountApp);
Notice: connect is from react-redux。
Define Router
Which Component should be rendered after receiving a url? It's defined by router.
This app has only one page, so we don't need to modify the router part.
app.router(({history}) =>
<Router history={history}> <Route path="/" component={HomePage} /> </Router> );
Notice:
-
historyis default hashHistory with_kparams. It can be changed to browserHistory, or remove_kparams with extra configuration.
Refresh page in browser, if success, you will see page below.
Add StyleSheet
We define stylesheet in css modules, which doesn't have many differences from normal css. Because we have already hooked className in Component, at this moment, we only need to replace index.less with follow content:
.normal {
width: 200px;
margin: 100px auto; padding: 20px; border: 1px solid #ccc; box-shadow: 0 0 20px #ccc; } .record { border-bottom: 1px solid #ccc; padding-bottom: 8px; color: #ccc; } .current { text-align: center; font-size: 40px; padding: 40px 0; } .button { text-align: center; button { width: 100px; height: 40px; background: #aaa; color: #fff; } }
Result.
Async Logic
Prior to this, all of our operations are synchronous. When clicking on the + button, the value is incremented by 1.
Now we have to dealing with async logic. dva process side effect( async logic ) with effects on model, which is executed based on redux-saga, with generator syntax.
In this app, when user clicked the + button, value will plus 1, and trigger a side effect, that is, minus 1 after 1 second.
app.model({
namespace: 'count',
+ effects: {
+ *add(action, { call, put }) {
+ yield call(delay, 1000); + yield put({ type: 'minus' }); + }, + }, ... +function delay(timeout){ + return new Promise(resolve => { + setTimeout(resolve, timeout); + }); +}
Notice:
-
*add() {}is equal toadd: function*(){} -
callandputare effect commands from redux-saga.callis for async logic, andputis for dispatching actions. Besides, there are commands likeselect,take,fork,cancel, and so on. View more on redux-saga documatation
Refresh you browser, if success, it should have all the effects of beginning gif.
Subscribe Keyboard Event
After implemented mouse click speed test, how to implement keyboard click speed test?
There is a concept called Subscription from dva, which is from elm 0.17.
Subscription is used for subscribe a data source, then dispatch action if needed. The data source could be current time, websocket connection from server, keyboard input, geolocation change, history router change, and so on.
Subscription is in model.
+import key from 'keymaster';
...
app.model({
namespace: 'count',
+ subscriptions: {
+ keyboardWatcher({ dispatch }) { + key('⌘+up, ctrl+up', () => { dispatch({type:'add'}) }); + }, + }, });
Here, we don't need to install keymaster dependency manually. When we write import key from 'keymaster'; and save, dva-cli will install keymaster and save to package.json. Output like this:
use npm: tnpm
Installing `keymaster`...
[keymaster@*] installed at node_modules/.npminstall/keymaster/1.6.2/keymaster (1 packages, use 745ms, speed 24.06kB/s, json 2.98kB, tarball 15.08kB)
All packages installed (1 packages installed from npm registry, use 755ms, speed 23.93kB/s, json 1(2.98kB), tarball 15.08kB)
2/2 build modules
webpack: bundle build is now finished.
All Code Together
index.js
import dva, { connect } from 'dva'; import { Router, Route } from 'dva/router'; import React from 'react'; import styles from './index.less'; import key from 'keymaster'; const app = dva(); app.model({ namespace: 'count', state: { record: 0, current: 0, }, reducers: { add(state) { const newCurrent = state.current + 1; return { ...state, record: newCurrent > state.record ? newCurrent : state.record, current: newCurrent, }; }, minus(state) { return { ...state, current: state.current - 1}; }, }, effects: { *add(action, { call, put }) { yield call(delay, 1000); yield put({ type: 'minus' }); }, }, subscriptions: { keyboardWatcher({ dispatch }) { key('⌘+up, ctrl+up', () => { dispatch({type:'add'}) }); }, }, }); const CountApp = ({count, dispatch}) => { return ( <div className={styles.normal}> <div className={styles.record}>Highest Record: {count.record}</div> <div className={styles.current}>{count.current}</div> <div className={styles.button}> <button onClick={() => { dispatch({type: 'count/add'}); }}>+</button> </div> </div> ); }; function mapStateToProps(state) { return { count: state.count }; } const HomePage = connect(mapStateToProps)(CountApp); app.router(({history}) => <Router history={history}> <Route path="/" component={HomePage} /> </Router> ); app.start('#root'); // --------- // Helpers function delay(timeout){ return new Promise(resolve => { setTimeout(resolve, timeout); }); }
Build
Now that we've written our application and verified that it works in development, it's time to get it ready to deploy to our users. To do so, run the following command:
$ npm run build
Output.
> @ build /private/tmp/dva-quickstart
> atool-build
Child
Time: 6891ms
Asset Size Chunks Chunk Names
common.js 1.18 kB 0 [emitted] common
index.js 281 kB 1, 0 [emitted] index
index.css 353 bytes 1, 0 [emitted] index
After build success, you can find compiled files in dist directory.
What's Next
After complete this app, do you have answer of all the questions in the beginning? Do you understand this concepts in dva, like model, router, reducers, effects and subscriptions ?
Next, you can view dva official library for more information.
https://github.com/dvajs/dva/blob/master/docs/GettingStarted.md
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