React to learn new features

1 context

2 contextType

3 lazy

4 suspense

5 memo

===========

1 Context provides a way to allow data transfer without a manual transmission in a tree assembly

 

API： createContext(defaultValue)

Example 1:

React Import, the Component {,} from the createContext 'REACT'; // here function derived context 
Import logo from './logo.svg' ; 
Import './App.css' ; 

const BatteryContext = the createContext (); // in Create a context where 

// grandchildren component 
class the extends the component {Leaf 
    the render () { 
        // defined here consumer consumer 
        return (
             <BatteryContext.Consumer> 
            { 
                Battery => <h1 of> BatteryName: Battery {} </ h1 of>
             }
             </ BatteryContext.Consumer>
         ) 
    } 
} 

// subassembly
{Middle the extends the Component class 
    the render () { 
        return <Leaf />;
     } 
} 

// parent element 
class the extends the Component {the App 
    the render () { 
        // defined here Provider context provider 
        return (
             <60 BatteryContext.Provider value = { }> 
                <Middle /> 
            </BatteryContext.Provider>         ) 
    } 
} 
Export default the App;