I flagged Split Textarea input text into all textarea box without enter button. for migration to Stack Overflow since that site doesn't appear in the migration path in the close dialog, and only moderators can perform the desired migration. However, my flag was declined.
As the link to W3 Schools and the first comment suggest, it's a technical question rather than a math one, so it shouldn't have been posted. Nonetheless, given that it's already there, a usual and helpful suggestion would be to migrate this to another suitable SE site, so that SE doesn't lose content, and that OP would probably receive answers from good hands. (I've asked some questions on Stack Overflow, and received several great answers.)
If we let it sit there, it's going to be auto-deleted as "RemovedAbandonedClosed" (or deleted by three votes), and that won't add value to the site.