Recording response from a side by side question

I want to record the response from a side by side matrix, I used the code "var response=document.getElementById( 'QR~QID422#1~1' )" - however, i am not getting the response stored in the variable - Can you help ? While trying multiple options for fixing the issue - I created a simple multiple choice with a drop down list and tried to capture the response var order=document.getElementById( 'QR~' + qid2 + '~1' ) - But I get only "null" as a response and not getting the value captured. Where am I missing ?