Parse Error:Adjacent JSX elements must be wrapped in an enclosing tag(React.js )

Question

I am trying to set up my React.js app so that it displayed my big menu tree.

The way my render function is set up looks like:

    let menuTitle = ['受注数入力業務', '発注数入力業務', '各店発注数入力業務', '売仕搬入数入力業務', '実在庫数入力業務', '非定型伝票引渡し業務', '通常反品数入力業務', '雑搬入数入力業務', '発注数入力業務', '帳票出力／マスタ管理'];
    
    const menuSubTitele = new Map();

    menuSubTitele.set('受注数入力業務', ['01.受注数入力', '02.受注補正数入力', '03.チェックリスト確定', '04.受注データFD読込', '05.チェックリスト', '06.チェックリストⅡ', '07.受注データFD読込エラーリスト'])
    menuSubTitele.set('発注数入力業務', ['11.発注数入力', '12.発注数キャンセル', '13.チェックリスト', '14.チェックリストⅡ', '15.注文書出力'])
    menuSubTitele.set('各店発注数入力業務', ['51.各店発注数入力', '52.注文書出力', '53.チェックリスト'])
    menuSubTitele.set('売仕搬入数入力業務', ['21.売仕搬入数入力', '22.チェックリスト'])
    menuSubTitele.set('実在庫数入力業務', ['41.実在庫数入力', '42.チェックリスト'])
    menuSubTitele.set('非定型伝票引渡し業務', ['71.雑介入数入力', '72.非定型伝票引渡し明細出力'])
    menuSubTitele.set('通常反品数入力業務', ['31.返品数入力', '32.チェックリスト', '33.返品伝票出力', '34.チェックリストⅡ'])
    menuSubTitele.set('雑搬入数入力業務', ['81.雑搬入数入力', '82.チェックリスト'])
    menuSubTitele.set('発注数入力業務', ['61.返品数入力', '62.チェックリスト', '63.返品伝票出力', '64.チェックリストⅡ'])
    menuSubTitele.set('帳票出力／マスタ管理', ['90.帳票出力メニュー', '91.マスメ保守ニュー', '92.マスタ一覧メニュー', '93.マスタ管理メニュー'])

return ( 
       <div className='App'>
        <Drawer anchor={'left'} open={state['left']} onClose={toggleDrawer('left', false)}>      
        <List aria-label='secondary mailbox folders'  className = "leftMenu">
        {menuTitle.map((name) => (  
        <ListItem button onClick={handleClick}>{`${name}`}
        　{open ? <ExpandLess /> : <ExpandMore />}
        </ListItem>
          <Collapse in={open} timeout="auto" unmountOnExit>
          <List component="div" disablePadding>
                {menuSubTitele[0].map((item) => (
                <ListItemLink to='' primary={`${item}`} /><Divider light />   
                ))}   
          </List>
          </Collapse>               
        ))}
        </List>   
        </Drawer>
   </div>);

But when running this, I get the error in the question:

Parsing error: Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>?

  |         　{open ? <ExpandLess /> : <ExpandMore />}
  |         </ListItem>
> |           <Collapse in={open} timeout="auto" unmountOnExit>
  |           ^
  |           <List component="div" disablePadding>
  |                 {menuSubTitele[0].map((item) => (
  |                 <ListItemLink to='' primary={`${item}`} /><Divider light />   ```

I understood, that my map-function in HTML was breaking JSX Parsing , but have no any idea how fix it.

Answer 1

you can't map over more than one element unless you wrap them in a parent element. To clarify, you've mapped over <ListItemLink to='' primary={${item}} /><Divider light /> without wrapping them in a parent element and this results an error.

Answer 2

Try enclosing the mapped elements either in a div or a React.Fragment

<List component="div" disablePadding>
  {menuSubTitele[0].map((item) => (
   <React.Fragment>
      <ListItemLink to='' primary={`${item}`} /><Divider light />
   </React.Fragment>)
  )}