Here's a simple way of getting form field data from a SharePoint form, adding that data to a URL, and then causing the browser to navigate to that URL. It assumes a form named MyForm and a textbox element named TextBox1. Additional parameters can be added as needed. This gets you started:
References
function setMyFormURL() { var string = document.getElementById('Textbox1').value; var urlString = '~/sitepages/myFile.aspx?fn=' + string; document.location.href = urlString; } . . . OnClientClick='JavaScript:setMyFormURL();return false;'
References