样式控制 & classnames工具优化类名控制   
  
 
const  style =  { color:  'red' , fontSize:  '30px' 
} function  App ( )  { return  ( < div className= "App" > { } < p style= { style} > Hello BLU ! < / p> < / div> ) ; 
} 
export  default  App; 
import  './index.css' ; function  App ( )  { const  clickHandler  =  ( name )  =>  { alert ( "Hello "  +  name) ; } return  ( < div className= "App" > { } < button className= 'bluBtn'  onClick= { ( )  =>  clickHandler ( 'BLU' ) } > Click Me< / button> < / div> ) ; 
} 
export  default  App; 
.bluBtn  { color :  red; font-size :  20px; font-weight :  600; 
} 
npm  install  classnames
import  './index.css' ; 
import  classNames from  'classnames' ; 
import  {  useState }  from  'react' ; function  Tab ( )  { const  [ type,  setType]  =  useState ( '' ) ; const  handleTabClick  =  ( name )  =>  { setType ( name) ; } return  ( < div> < button className= { classNames ( 'bluBtn' ,  { active:  type ===  'A' } ) }  onClick= { ( )  =>  handleTabClick ( 'A' ) } > Tab A < / button> < button className= { classNames ( 'bluBtn' ,  { active:  type ===  'B' } ) }  onClick= { ( )  =>  handleTabClick ( 'B' ) } > Tab B < / button> < / div> ) ; } 
export  default  Tab; 
.bluBtn  { color :  red; font-size :  20px; font-weight :  600; 
} 
.bluBtn.active  { background-color :  bisque; 
} 
import  Tab from  "./Tab" ; function  App ( )  { return  ( < div className= "App" > < Tab> < / Tab>       < / div> ) ; 
} 
export  default  App;