The dirName property of the HTMLTextAreaElement interface is the directionality of the element. It reflects the value of the <textarea> element's dirName attribute. This property can be retrieved or set.
The dirname attribute controls how the element's directionality is submitted. When included, the form control will submit with two name/value pairs: the first being the name and value of the <textarea>, and the second being the value of the dirname attribute as the name, with a value of ltr or rtl as set by the browser.
A string. The direction of the element.
textareaElement.dirName = "rtl";