将map函数的所有返回值放在一个div with scrollit样式类中，并将以下代码添加到CSS中：

.scrollit {
    overflow:scroll;
    height:100px;
}

您代码如下所示：

return (
    <div className='journaltable-div'>
    <table className='table table-journal'>
        <thead className='table-head'>
            <tr className='table-head-row'>
                <th>Task</th>
                <th>Date-created</th>
                <th>Action</th>
            </tr>
        </thead>
        <tbody className='table-body'>
         <div className="scrollit">
           { journalList.map((entry) => {
                const { key, journal, time } = entry
                return (
                    <tr key={key} className="table-body-row">
                        <td>{journal}</td>
                        <td>{time}</td>
                        <td><button 
                            className='button button-complete'
                        onClick={(e) => {
                            e.stopPropagation
                            addToLog(key, "completed")
                            removeJournal(key)
                        }}>completed</button><button 
                            className='button button-delete'
                        onClick={(e) => {
                            e.stopPropagation
                            addToLog(key, "deleted")
                            removeJournal(key)
                        }}>delete</button></td>
                    </tr>
                )
            }) }
         </div>     
        </tbody>
    </table>
    <div className='redirect-div'>
        <button  className='redirect-logs'  style={{cursor: 'pointer'}} onClick={() => {handleLogs()}}> Check Logs</button>
    </div>
</div>