Calling Google Apps Script from a Chrome Extension - google-chrome-extension

Question

I know similar questions have been asked here before, but I didn't find an answer that helped me. Sorry for that! I'm probably just too inexperienced to understand those answers, so please bear with me.
I have written a Google Apps Script that scans a specific Spreadsheet (not authored by me, but I can view) and counts certain fields. The doGet(e) function returns the count, so when I run the published-as-web-app I see a number.
Now from my background.js in my chrome extension I did something like this:
var my_app = "https://script.google.com/a/macros/google.com/s/.../exec?param=value";
var xhr = new XMLHttpRequest();
try {
xhr.open("GET", my_app);
xhr.send(null);
var result = xhr.getAllResponseHeaders();
localStorage.count = result;
chrome.browserAction.setBadgeText({text: localStorage.count});
} catch(e)
...
}
This is very rough, since I'm very new to JavaScript and Chrome Extensions and such.
I'm guessing getAllResponseHeaders() is not how I get to the resulting number that is displayed when calling my_app, so what should I use instead? In the API reference for XMLHttpRequest I didn't find anything obvious.
I'm pretty sure there's a lot more wrong with my code, but let's go one step at a time.
Thanks already in advance! Detailed answers would be great, so I can follow them and extend my currently very limited knowledge.

Answer 1

If you are making an HTTP Request from client side JavaScript to Apps Script, then you can use something like this:
function requestToAppsScript() {
if (window.XMLHttpRequest) {
// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
} else { // code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function() {
//console.log('xmlhttp.readyState: ' + xmlhttp.readyState);
if (xmlhttp.readyState===4 && xmlhttp.status===200) {
//console.log('xmlhttp.responseText: ' + xmlhttp.responseText);
var theReturnData = xmlhttp.responseText;
//console.log('return value: ' + theReturnData);
};
};
xmlhttp.open("GET","URL here",true);
xmlhttp.send();
};

Answer 2

basically I just didn't parse the output right. The output I received contained a lot of things and the number I was looking for was hidden in that mess of a string, always behind some string called "cajaHtml".
Therefore the call is now:
xhr.open("GET", my_app);
xhr.onreadystatechange = handleResponse;
xhr.responseType = "text";
xhr.send(null);
with
function handleResponse() {
if (xhr.readyState == 4) {
var result = xhr.responseText.split("cajaHtml")[1];
}
}
Thanks!