script.js

if (document.URL.includes("games/")) {
  console.log("game page detected")
  var headerParse = document.URL.split("/")
  //console.warn(headerParse)
  var gid = headerParse[4]
  console.log("gid: " + gid)
  var req = new XMLHttpRequest();
  if (gid != null) {
    chrome.runtime.sendMessage({game_id: gid}, null, function(response) {})
  }
}

chrome.runtime.onMessage.addListener(function (request, sender, sendFunc){
    // filtered servers
    console.log(request)
    var json = JSON.parse(request)
    // we have servers
    // add buttons
    var parent = document.getElementById("game-instances")  
    var titleNode = document.createElement("H1")
    var titleText = document.createTextNode("SLS Server List")
    titleNode.appendChild(titleText)
    var titlebreak1 = document.createElement("br")
    var titlebreak2 = document.createElement("br")
    parent.appendChild(titlebreak1)
    parent.appendChild(titleNode)
    parent.appendChild(titlebreak2)
    if (json.length == 0) {
      console.log("empty server list")
      var notifyNode = document.createElement("H3")
      var notifyText = document.createTextNode("No servers are currently running or this game does not use SLS or is not in the repository.")
      notifyNode.appendChild(notifyText)
      parent.appendChild(notifyNode)
    } else {
      for (var index = 0; index < json.length; index++) {
        var element = json[index];
        console.log(element)
        var button = document.createElement("button")
        button.setAttribute("OnClick", "Roblox.GameLauncher.joinGameInstance(" + element.placeId + ", \"" + element.serverId + "\")")
        var linebreak = document.createElement("br")
        var text = document.createTextNode("Press to join server! (amount of players: " + element.registeredPlayerCount + ")")
        button.appendChild(text)
        parent.appendChild(button)
        parent.appendChild(linebreak)      
      }
    }
})