Appending To A URL From A Form Field

I have a basic text input field that is validated with jquery.

I've created a function to append to a url once the user has input an ID into the text field.

However, when I use the window.open method, a new window opens, and when I use window.location, the user ID is appended to the current url and not the url defined in the function.

Here is the function:

Here is the markup:

When a user clicks on the 'submit' button without entering anything into the text field, a new window opens (I know, the function uses the window.open), when I close the new window - the jquery works, a label saying 'this field is required' appears.

When a user inputs an ID, and then clicks on the 'submit' button, a new window opens with the correct appended url.

What I need to have happen is - if the text field is empty and the user clicks on the 'submit' button - I don't want the function to run.

When I switch window.open to window.location, then when the user inputs an ID into the text field, that ID is appended to the CURRENT url and not the url specified in the function. I don't have the luxury of server side scripting.