Most rich text editors for the web use JavaScript. These are some popular ones you could consider
- jwysiwig
- markitup
- Redactor (This is great jQuery based wysiwyg editor that also has a Rails extension I’ve linked to below.)
- Bootstrap-wysihtml5 (If you’re looking for a Twitter Bootstrap style editor)
Of course, you could also consider heavy-weight alternatives like TinyMCE or CKEditor, if your needs are such.
Ruby on Rails Solutions
If you need to able add images to your textarea through a Ruby on Rails library, such as Paperclip or Carrierwave, you may consider one of these
- rails-ckeditor
- Mercury (Railscast)
- rails_tiny_mce
- redactor-rails
The Problem with using a usual JavaScript Editor
Most javascript editors will prompt for a URL when you try to add an image to your textarea, so if you need to do so, you may have to upload the image elsewhere and provide the editor with the URL.
There is however one JavaScript editor I found, http://nicedit.com/, that does an AJAX upload to http://imageshack.us when you add an image. Of course, the images that are served will become totally dependent on imageshack which may or may not work for you. It really depends on your scenario.