how to Send data from html page to process in javascript?

Question

I need to process data strings and numbers in javascript but I don't know how to do that!
Am I need form elements? and what should be in action attribute?

Answer 1

document.formName.formElementName.value

Answer 2

or document.getElementById(id)

Answer 3

Javascript could get any data information (form input or other elements) from a linked HTML.

Javascript access the HTML elements
by its ID using getElementById() function or
by its CLASS using getElementsByClassName() or
by its TAG using getElementsByTagName()

Please check out MDN web docs or w3schools for more information.