An Introduction to ReactJS
Post on 09-Jul-2015
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An Introduction to ReactJAMES PEARCE@jamespearce
toddler
imperative programming
describe computation in terms of statements that change a
program state
teenager
declarative programming
express the logic of a computation without
describing control flow
A JavaScript Library ForBuilding User Interfaces
http://todomvc.com/
☕(n)
Simple !
Declarative
http://reactjs.org
state describe
state describe
for every change of
the whole user interface
state describe
for every change of
the whole user interface
state 1 state 2
state 1 state 2
DOM mutations
MVD #1
* Minimum Viable Demo
<!DOCTYPE html> <html> <head> <script src="react/build/react.js"></script> <script src="react/build/JSXTransformer.js"></script> <script src="labelapp.js" type="text/jsx"></script> </head> <body/> </html>
var LabelApp = React.createClass({ render: function () { return <div>Hello World!</div>; } }); !React.render( <LabelApp />, document.body );
var LabelApp = React.createClass({ render: function () { return <div>{this.props.message}</div>; } }); !React.render( <LabelApp message="Hello Raleigh!" />, document.body );
State & component lifecycle
props !
passed in from parent !
<MyComp foo="bar" />
this.props read-only within !
can be defaulted & validated
state !
created within component !
getInitialState
this.state to read
this.setState() to update
var MyComponent = React.createClass({ ! propTypes: {}, getDefaultProps: function () {}, getInitialState: function () {}, ! componentWillMount: function () {}, componentWillUnmount: function () {}, ...
render: function () { // only read props & state -> return UI }, });
var MyComponent = React.createClass({ ! iGotClicked: function () {...}, ! render: function () { return <div onClick={this.iGotClicked}>Click</div>; }, });
Or a parent’s method passed in via props
MVD #2
var LabelApp = React.createClass({ getDefaultProps: function () { return {message: 'Hello World!'}; }, ! getInitialState: function () { return {message: this.props.message}; }, ! render: function() { return <div>{this.state.message}</div>; } });
onClick: function () { this.setState({message: 'Hello Raleigh!'}); }, !render: function () { return ( <div onClick={this.onClick}> {this.state.message} </div> ); }
How does data flow?
Component
Component
Component
Component
Component Component
props
props
setState
Component
Component
Component
Component
Component Component
props
props
setState
eventcallback
statestored as high up as it needs to be to pass down to affected children
Table
Row Cell Cell Cell Cell
Row Cell Cell Cell Cell
Row Cell Cell Cell Cell
state ison cells
Table
Row Cell Cell Cell Cell
Row Cell Cell Cell Cell
Row Cell Cell Cell Cell
Total
Total
Total
state ison rows
Table
Row Cell Cell Cell Cell
Row Cell Cell Cell Cell
Row Cell Cell Cell Cell
Total
Total
Total
Row Total Total Total Total Total
state ison table
MVD #3
var Table = React.createClass({ getInitialState: function () { var data = []; for (var r = 0; r < this.props.rows; r++) { data[r] = []; for (var c = 0; c < this.props.columns; c++) { data[r][c] = 0; } } return {data: data}; }, render: function () {return <table>...</table>;} }); !React.render(<Table columns={4} rows={3} />, ...
var Row = React.createClass({ render: function () { return <tr>{this.props.children}</tr>; } }); !var Total = React.createClass({ render: function () { return <th>{this.props.value}</th>; } });
var Cell = React.createClass({ onChange: function (e) { this.props.onChange( this.props.row, this.props.column, parseInt(e.target.value) || 0 ); }, render: function () { return (<td> <input type="number" value={this.props.value} onChange={this.onChange} /> </td>); }, });
var Table = React.createClass({ onCellChange: function(row, column, value) { this.state.data[row][column] = value; this.setState({data: this.state.data}); }, ! render: function() { // for rows & columns, append <Row>s containing // <Cell row={r} column={c} // value={this.state.data[r][c]} // onChange={this.onCellChange} /> // // also append to each row and in a final row: // <Total value={total} /> }, ...
Component-based UI Virtual DOM
Uni-directional data flow
“Give it 5 minutes”
http://reactjs.org
JAMES PEARCE@jamespearce
https://www.flickr.com/photos/matthewpaulson/6773801511 https://www.flickr.com/photos/johnath/5358512977
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