$.ajax async response usage

Hello,

I have spent hours on this issue, which seems to trip up lots of newbies.

I am trying to test to see if a file exists and execute something if the file exists, and write to the console log the error if there is an error.

Thank you,

Stuart

function UrlExists(filename)
{
  console.log("arrive in async function")
  var apple= $.ajax({
    type: "HEAD",
    async: false,
    url: filename
  })
  return apple;
}