eSix_UserQuickSearch

var pagno = 1; // Current page

var req = new XMLHttpRequest();
req.onreadystatechange=function() {
  if(req.readyState==4 && req.status==200)
    gotIt(req.responseText);
}

function request() { // Use an URL to help narrow even more the results instead of searching in the entire database
  var url = "http://e621.net/user/index.json?name="+escape(serch)+"&page="+pagno+"&order=name&level=-1";
  req.open("GET",url,true);
  req.send();
}

function gotIt(text) {
  if(text==="[]") { // No more pages
    // Notify that the specified user couldn't be found
    alert("User \""+serch+"\" does not exist");
  } else {
    var users = eval("("+text+")");
    var uname = "";
    var pos = 0;

    while(uname!=serch && pos<users.length) {
      uname = users[pos].name;
      pos++;
    }

    if(uname===serch)
      alert("\""+serch+"\" found at index "+pos+" on page "+pagno);
    else { // Advance to the next page and search again
      pagno++;
      request();
    }
  }
}

var serch = "e621"; // Username to look for (case sensitive)
request();