I use tinymce for a webpage that dynamically generates at least 5 texts. The configuration I use only works on the first textarea unfortunately.
textarea
According to tinymce.com/wiki.php/Configuration:selector, selector is the recommended way of selecting what elements should be editable.
For all textarea elements, as requested:
selector: "textarea",
Or more elegantly, only those elements with a specific CSS tag:
selector: "textarea.editme",