Request simple Javascript coding help

this project must be done in an hour [login to view URL] in this part i'm trying to choose a URL and picture at random when the window opens +picture+ is my attempt at a variable return "[login to view URL] 98702bf97a021ddc14d&attachment={%22name%22:%20%22G edd%22,%22href%22:%20%22+keyword+%22,%22descriptio n%22:%20%22Tos!%22,%22caption%22:%20%22%22,%22medi a%22:%20[{%22type%22:%20%22image%22,%22src%22:%20%22+pictur e+%22,%22href%22:%20%22+keyword+%22}]}"