如何将1页的下拉值传递给bootstrap模式？

I have a dropdown with a list of values. When user selects 1 from the dropdown and click on a button, a bootstrap modal pops up. I want to pass the dropdown value to the pop up. I know how to do this with 2 different html pages. But can anyone help how to pass the value to the modal.I have a dropdown with a list of values. When u