Why does the following XMLHttpRequest return undefined?
function fetchFileList(){
    var request = new XMLHttpRequest();
    request.open("GET","../files.json",false);
    request.onload = function(){
        if(request.status == 200){
            return request.responseText;
        }
    }
    request.send();
}
, but if I console.log() request.responseText, the console outputs what it's supposed to: 
if(request.status == 200){
            console.log(request.responseText);
            return request.responseText;
        }
Thanks.
