[Final] ReactJS presentation

CONTENT
• Introduction React JS and JSX
• Component, State, Props.
• Life Cycle of Component
• Pros & Cos
• Demonstration

WHAT IS REACT?
• A JavaScript Library For Building User Interfaces
• Renders your UI and responds to events.
• It also uses the concept called Virtual DOM, creates an in-memory data structure
cache, enumerates the resulting differences, and then updates the browser’s
displayed DOM efficiently.
• One of the unique features of React.js is not only it can perform on the client side, but
it can also be rendered on the server side, and they can work together interoperably.

Angular has
• modules
• controllers
• directives
• scopes
• templating
• linking functions
• filters
• dependency injection
WHAT IS REACT?

Angular has JUST COMPONENT
• modules
• controllers
• directives
• scopes
• templating
• linking functions
• filters
• dependency injection
WHAT IS REACT?

#2 Single Source of Truth
MVC proposes that your Model
is the single source of truth—
all state lives there. Views
are derived from the Model,
and must be kept in sync.
When the Model changes, so
does the View.
WHAT IS REACT?

does the View.
WHAT IS REACT?
I AM DOUBLE-EDGED SWORD

does the View.
WHAT IS REACT?
I AM DOUBLE-EDGED SWORD
Only render when state
changed

WHAT IS REACT? – VIRTUAL DOM
• Manipulate DOM is high cost.
• React first assembles the entire structure
of your app in-memory, using those
objects. Then, it converts that structure
into actual DOM nodes and inserts them
in your browser’s DOM.

WHAT IS REACT? – VIRTUAL DOM
<script>
var helloEl = React.createElement(
'div',
{ className: 'hello' },
'Hello, world!‘
);
React.render(helloEl,document.body);
</script>

JSX
• JSX = Javascript + XML.
const element = <h1>Hello, world!</h1>;

JSX
<script>
var helloEl = React.createElement('div', { className: 'hello' }, 'Hello,
world!');
React.render(
helloEl,
document.body
);
</script>
<script type="text/jsx">
var helloEl = <div className: "hello">Hello, world!</div>;
React.render(
helloEl,
document.body
);
</script>

COMPONENT
• Components let you split the UI into independent, reusable pieces, and think about
each piece in isolation.
• Conceptually, components are like JavaScript functions. They accept arbitrary inputs
(called "props") and return React elements describing what should appear on the
screen.

COMPONENT
class TodoInput extends React.Component {
render() {
return (
<div className="form-inline">
<input className="form-control" type="text" value={this.state.content}
onChange={this.updateState}/>
</div>
);
}
}

COMPONENT - PROPS
• Props is what you pass into the Component via attributes.
• Props is the only way to input data. (Or you can use Redux).
• Props are immutable.
• Container component will define data that can be changed
• Child Component will received data from parent component via props.

COMPONENT - PROPS
import React from 'react';
class App extends React.Component {
render() {
return (
<div>
<h1>{this.props.headerProp}</h1>
<h2>{this.props.contentProp}</h2>
</div>
);
}
}
export default App;
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App.jsx';
ReactDOM.render(
<App headerProp="Header from props..."
contentProp="Content from props..."/>,
document.getElementById('app')
);
export default App;

COMPONENT - STATE
• Private data of component
• When change -> Re-render Component
• Can’t read from outside Component

COMPONENT - STATE
constructor(props) {
super(props); //Call this function because 'this' is not allowed before super().
this.state = {
content: ''
};
this.addTodo = this.addTodo.bind(this);
}
updateState(e) {
this.setState({content: e.target.value});
}
addTodo() {
// We of course not declare onSave function of this component at parent component
// Refer to: Body.jsx for more information
// We declare this onSave at mapDispatchToProps function
this.props.onSave.call(this, this.state.content, this.props.todo && this.props.todo.id || null);
this.setState({
content: ''
})
}
render() {
return (
<div className="form-group">
<input className="form-control" type="text" value={this.state.content} onChange={this.updateState}/>
</div>
</div>
);
}
}
constructor(props) {
super(props); //Call this function because 'this' is not allowed before super().
this.state = {
content: ''
};
this.addTodo = this.addTodo.bind(this);
}
updateState(e) {
this.setState({content: e.target.value});
}
addTodo() {
// We of course not declare onSave function of this component at parent component
// Refer to: Body.jsx for more information
// We declare this onSave at mapDispatchToProps function
this.props.onSave.call(this, this.state.content, this.props.todo && this.props.todo.id || null);
this.setState({
content: ''
})
}
render() {
return (
<div className="form-group">
<input className="form-control" type="text" value={this.state.content} onChange={this.updateState}/>
</div>
</div>
);
}
}

REACT COMPONENT LIFECYCLE
• React enables to create components by invoking the React.createClass() method
which expects a render method and triggers a lifecycle that can be hooked into via a
number of so called lifecycle methods.
• This short article should shed light into all the applicable functions.
• Understanding the component lifecycle will enable you to perform certain actions
when a component is created or destroyed. Further more it gives you the
opportunity to decide if a component should be updated in the first place and to
react to props or state changes accordingly.

THE LIFECYCLE -
INITIALIZATION
• Occurs when the component is created.
var Greeting = React.createClass({
propTypes: {
name: React.PropTypes.string
},
getDefaultProps: function () {
return {
name: 'Mary'
};
},
getInitialState: function () {
return {
helloSentence: 'Hello'
}
}
// ...
});

THE LIFECYCLE -
INITIALIZATION
• getDefaultProps and getInitialState not exists when
define Component as Class ES6.
Greeting.defaultProps = {
name: 'Mary'
};
constructor(props){
super(props);
this.state = {
name: 'Mary'
}
}

THE LIFECYCLE -
INITIALIZATION
• Inside ComponentWillMount, setting state won’t
trigger re-render whole component.
• We CAN NOT modify state in render method.
• DOM Manipulation is only permitted inside
componentDidMount method.

THE LIFECYCLE -
STATE CHANGES
• Occur when state is changed (via this.setState(..))
except inside componentWillMount methods
shouldComponentUpdate: function(nextProps, nextState){
// return a boolean value
return true;
}
• shouldComponentUpdate returning false results in
followed methods won’t be triggerd also.
• shouldComponentUpdate won’t triggered in the
initial phase or when call forceUpdate().
• Current State of Component DID NOT have new
value,

THE LIFECYCLE -
PROPS CHANGES
• Occurs when data passed from parent component to
child component changed (via props).
• Changing states in ComponentWillReceiveProps DID
NOT trigger re-render component.
componentWillReceiveProps: function(nextProps)
{
this.setState({
// set something
});
}
Props Change  componentWillReceiveProps trigged
Props Change  componentWillReceiveProps trigged
NOT

THE LIFECYCLE -
UNMOUNTING
• Used to clean up data

PROS & COS OF REACT.JS
THE GOOD POINTS:
• React.js is extremely efficient
- Virtual DOM
• It makes writing Javascript easier
- React.js uses a special syntax called JSX
• It gives you out-of-the-box developer
tools
- React.js chrome extension
• It’s awesome for SEO
- Server rendering
• UI Test Cases
THE BAD:
• React.js is only a view layer.
• There is a learning curve for beginners
who are new to web development.
• Library size. (~ Angular)

Why you should use React.js:
• React.js works great for teams, strongly enforcing UI and workflow patterns.
• The user interface code is readable and maintainable.
• Componentized UI is the future of web development, and you need to start doing it
now.
• And also, there is now a lot of demand for developers with ReactJS experience.

Why you should NOT use React.js:
• Slow you down tremendously at the start.
• You will reinvent a lot of wheels.

• Flux/Redux
• React Native
OUR NEXT STEPS

REFERENCES
• https://firstdoit.com/how-i-learned-to-stop-worrying-and-love-react-
4e22b0bb6c2a#.vt2mjxu6s
• https://offroadcode.com/journal/news/reactjs-whats-it-all-about/
• http://sixrevisions.com/javascript/why-i-ditched-angular-for-react/
• https://github.com/hpphat92/my-todo-reactjs
• https://hpphat.wordpress.com/category/web-dev/react/
• http://blog.andrewray.me/reactjs-for-stupid-people/
• 192.168.1.240sharePhat.HongReactjs

[Final] ReactJS presentation

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