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react-workshop-slides.html
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<!DOCTYPE html>
<html>
<head>
<title>Title</title>
<meta charset="utf-8">
<style>
@import url(https://fonts.googleapis.com/css?family=Lato);
@import url(https://fonts.googleapis.com/css?family=Ubuntu+Mono:400,700,400italic);
body {
font-family: 'Lato';
}
h1, h2, h3 {
font-family: 'Lato';
font-weight: normal;
}
.remark-code, .remark-inline-code {
font-family: 'Ubuntu Mono';
}
</style>
</head>
<body>
<textarea id="source">
class: center, middle
# React
Jarda Šnajdr @jsnajdr
---
### Resources
- https://github.com/jsnajdr/react-workshop
- https://jsnajdr.github.io/react-workshop-slides.html
---
### Quick Tour of ES2015/2016/2017
Use `let` and `const` to declare variables. No more `var`.
```js
const API_KEY = "12345";
let i = 0;
API_KEY = "67890"; // error
i++; // ok
```
---
Use template literals to format strings.
```js
for (let i = 0; i < 10; i++) {
console.log(`Iteration number ${i}: ${2 * i + 1}`);
}
```
---
Use destructuring to access object and array fields.
```js
const state = {
data: [ "a", "b", "c" ],
sortOrder: "asc"
};
const { data, sortOrder } = state;
let [ first, second ] = data;
console.log(sortOrder, first, second); // "asc", "a", "b"
```
---
Use `for...of` to loop through arrays (and other iterable objects).
```js
const items = [
{ id: 1 },
{ id: 2 },
{ id: 3 }
];
for (let item of items) {
console.log("item id:", item.id);
}
// Destructure!
for (let { id } of items) {
console.log("item id:", id);
}
```
---
Be functional! (with arrow functions)
```js
const numbers = [ 1, 2, 3, 4, 5, 6 ];
// Transform array into another array
const squares = numbers.map(n => n ** 2);
// Filter array values with a filtering function
const evens = squares.filter(n => n % 2 === 0);
// Reduce the array into one value
const sum = evens.reduce((a, n) => a + n, 0);
```
---
Use spread operator to work with function parameters ...
```js
function compute(power, ...numbers) {
return numbers.reduce((a, n) => a + n ** power, 0);
}
compute(1, 3, 4); // 7
compute(2, 3, 4); // 25
```
... and arrays ...
```js
const additional = [ "b", "c" ];
const full = [ "a", ...additional ];
```
... and destructuring arrays ...
```js
const numbers = [ 1, 2, 3, 4, 5, 6 ];
const [ first, second, , ...others ] = numbers;
```
... and with objects, too!
```js
const props = { name: "user", value: "jarda", className: "user-field" };
const { name, value, ...rest } = props;
const nextProps = { id: "user", ...rest };
```
---
Use default values for parameters and destructured variables
```js
function sort(data, order = "asc") {
// sort the data
}
function sendRequest(url, options = {}) {
const { method = "GET" } = options;
performRequest(method, url);
}
sendRequest("http://github.com/api/commits");
sendRequest("http://github.com/api/createRepo", "POST");
```
---
Use classes instead of functions with prototypes.
```js
class CommitList extends React.Component {
// instance property
state = { loading: false, data: [] }
constructor(props) {
super(props);
// construct
}
render() {
// render
}
}
```
---
Use new smart methods on arrays and objects.
```js
const colors = [ "red", "green", "blue" ];
colors.find(c => c.length > 3);
colors.findIndex(c => c.startsWith("g"));
colors.includes("purple");
const ages = { jarda: 10, honza: 15, martin: 20 };
Object.keys(ages).map(console.log);
Object.values(ages).map(console.log);
for (const [ name, age ] of Object.entries(ages)) {
console.log(`${name} is ${age} years old`);
}
```
---
### Let's create a React app!
```bash
npm i -g create-react-app
create-react-app react-example
cd react-example
npm start
```
What's inside?
- `index.html` document with some markup
- `index.js` that imports the `App` component and renders it
- `App.js` component that defines some markup to be shown
- some CSS styles
- a template for mocha test
---
### Components and JSX
Component has a `render` method that declares what should be on the screen.
```js
class App extends React.Component {
render() {
let h = "Home";
return (
<div className="app">
Go to <a href="/">{ h.toUpperCase() }</a>
</div>
);
}
}
```
The JSX markup is the same thing as:
```js
React.createElement(
"div",
{ className: "app" },
"Go to ",
React.createElement(
"a",
{ href: "/" },
h.toUpperCase()
)
);
```
---
### React UI is declarative
Describe what should be on the screen, not how to get there.
```js
const { loading, error, commits } = this.state;
return (
<div className="App">
<button onClick={this.onClick} disabled={loading}>Load</button>
{ error && <div className="alert">{ error }</div> }
{ loading && <div className="loading">loading...</div> }
{ commits && <pre>{ JSON.stringify(commits, null, 2) }</pre> }
</div>
);
```
---
### React UI is composable
Presentational (dumb) components with no state, just props.
```js
class AppComponent extends Component {
render() {
const { loading, error, commits, onLoad } = this.props;
return (
<div className="App">
<button onClick={onLoad} disabled={loading}>Load</button>
<ErrorMessage error={error} />
<LoadingIndicator loading={loading} />
{ commits && <CommitList commits={commits} /> }
</div>
);
}
}
```
Can be just a function, too!
```js
const AppComponent = ({ loading, error, commits, onLoad }) => (
<div className="App">
<button onClick={onLoad} disabled={loading}>Load</button>
<ErrorMessage error={error} />
<LoadingIndicator loading={loading} />
{ commits && <CommitList commits={commits} /> }
</div>
);
```
---
### Unidirectional flow of data and actions
<div style="text-align:center"><img src="state-chart.png"/></div>
Component is a function of type State => UI (Map operation)
State update is a function of type (State, Action) => State (Reduce operation)
---
### Redux - a simple state management library
- state is stored in a Redux store
- state is the single source of truth
- state can be changed only by dispatching an action
- reducer is a pure function of state and action and produces a new state
```js
function reducer(state, action) {
return newState;
}
let store = createStore(reducer, initialState);
store.dispatch(action);
```
- clients can read the (immutable) state
```js
let state = store.getState();
```
- clients can subscribe to store updates
```js
let sub = store.subscribe(state => { ... });
```
---
### `react-redux`
`Provider` is a wrapper component to provide context to children
```js
const App = () => (
<Provider store={store}>
<ConnectedToolbar />
<ConnectedList />
</Provider>
);
```
Decorator (HOC) `connect(mapStateToProps, mapDispatchToProps)(Component)`
```js
export ConnectedComponent = connect(
state => ({
isLoading: state.commits.isLoading,
isEmpty: state.commits.list.length === 0,
commits: sortAndFilterCommits(state.commits),
}),
dispatch => ({
reload: () => dispatch(reloadAction()),
sort: (order) => dispatch(sortAction(order)),
})
)(Component);
```
---
Learn more:
- https://facebook.github.io/react/ (React)
- http://redux.js.org/ (Redux)
- https://leanpub.com/understandinges6 (ES6)
- http://www.2ality.com/ (ES6 and beyond)
</textarea>
<script src="https://remarkjs.com/downloads/remark-latest.min.js"></script>
<script>remark.create();</script>
</body>
</html>