Access HTML form submitted value from a different javascript file?

I have two HTML files, call them x and y (and two javascript files, each of which corresponds to its respective HTML file - so x' and y'). I have a form with a textfield and submit button in x. I want to access the submitted data (the text that the user enters into the textfield in x and clicks the submit button) from y'. Is this possible? If so, how? Thanks in advance.