React Core Features

Here is a summary of the core features. We will cover each feature in detail throughout the examples.

JSX (JavaScript Syntax Extension)

JSX has a concise and familiar syntax for defining tree structures with attributes
JSX syntax needs to be transpiled to JavaScript (i.e. by Babel)
In contrast to JavaScript, JSX is statically-typed
JSX uses ES6 classes, which are similar to Java

One-way data flow

Properties are passed by the parent component to the child components
The properties are treated as immutable values
Child components should never directly modify any properties that are passed to them
PropTypes can be used for defining the type of each property that is passed to a given component. If a component receives an invalid value for a property, there will be a warning in the console. PropTypes are checked during runtime

Virtual DOM

React uses the Virtual DOM to create an in-memory copy of the browsers DOM
When changing the state of components, React updates the virtual DOM first
After that it computes the resulting differences, and updates the browser’s displayed DOM efficiently

Lifecycle methods

These methods can be overridden for each component, to run code during a specific lifecycle phase.

Mounting:
- constructor()
- componentWillMount()
- render()
- componentDidMount()
Updating:
- componentWillReceiveProps()
- shouldComponentUpdate()
- componentWillUpdate()
- render()
- componentDidUpdate()
Unmounting:
- componentWillUnmount()
Error handling (since React 16 – released September 2017):
- componentDidCatch()

We will explain these core features in more detail with a couple of code snippets in the next section.

Babel (ES5, ES6)

The JavaScript syntax that you will see in our examples is ECMAScript 6 (ES6) notation. If you need to run your web app inside older web browsers, you can use Babel (https://babeljs.io/) to transpile ES6 code to ES5. Here is an example how babel will transpile the ES6 arrow function to a regular ES5 function.

ES6 syntax	Transpiled to ES5 syntax
[1,2,3,4].map(n => n + 1);	[1,2,3,4].map( function(n) { return n + 1; } );

https://blog.codecentric.de/en/2017/11/developing-modern-offline-apps-reactjs-redux-electron-part-2-reactjs-basics/

巴特西

React Core Features