Hi sun,
Thank you for contacting Syncfusion support.
Yes, we can write CSS in javascript and it is also one of the ways to include CSS into HTML page. But, completely writing it using JavaScript is purely based on our individual preferences. However, we request you check following link for reference.
Also, we ask you to post your general query in public discussion forum such mozilla developer forum, stackoverflow, etc.. for reaching out to wide range of developer community.
Please get back to us if you have any queries related to Syncfusion components.
Regards,
Jesus Arockia Sankaran S