The problem of rendering objects to DOM under React

Novice react, recently has a problem
for example, there is an object

obj= {

a:[1,2],
b:[3,4],
c:[5]

}
component how to write render () {} to cycle render 

    <div>
        <div>a<div>
        <div>
            <div>1</div>
            <div>2</div>
        </div>
    </div>
    
     <div>
        <div>b<div>
        <div>
            <div>3</div>
            <div>4</div>
        </div>
    </div>
    
    <div>
        <div>c<div>
        <div>
            <div>5</div>
        </div>
    </div>
    ...
React.js javascript
Apr.11,2021 
{
    Object.keys(obj).map(key => {
        return (<div key={key}>
            <div>{key}<div>
            <div>
                {
                   obj[key].map(item => {
                       return <div>{item}</div>
                   }) 
                }
            </div>
        </div>)
    })
}

Previous: How do vue routes pass parameters? How to get the parameters on the second page

Next: About the @ media media query of sass and the scope of! global

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b42655-2c613.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b42655-2c613.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?