chrome extension read value problem - google-chrome-extension

Question

I'm building my chrome extension and I've got weird problem. This is script I'm running in background page:
function getOpenedTabs() {
var openedTabs = [];
chrome.windows.getAll({}, function(wins) {
for (var w in wins) {
if (wins[w].id !== undefined) {
chrome.tabs.getAllInWindow(wins[w].id, function(tabs) {
for (var t in tabs) {
if (tabs[t].id !== undefined) {
openedTabs.push(tabs[t]);
}
}
});
}
}
});
return openedTabs;
}
chrome.tabs.onCreated.addListener(function(tab){
var openedTabs = getOpenedTabs();
var length = openedTabs.length;
console.log("Quantity of tabs: " + length );
if (length > 20) {
openedTabs.sort(function(a,b){return a.visitCount - b.visitCount});
var t = openedTabs.shift();
chrome.tabs.remove(t.id);
console.log("The extension closed the " + t.title + " tab");
}
});
In debugging mode openedTabs.length returns correct value. But when I removed all breakpoints then openedTabs.length returns zero all time.
What kind of problem it might be?
Thanks.

Answer 1

Chrome API calls are asynchronous (think ajax calls), so they are not executed in order. You can't return from such methods, you need to use callbacks.
function getOpenedTabs(callback) {
chrome.windows.getAll({populate: true}, function(wins) {
var openedTabs = [];
for (var w=0; w<wins.length;w++) {
for (var t=0;t<wins[w].tabs.length;t++) {
if (wins[w].tabs[t].id !== undefined) { //I don't think this check is needed
openedTabs.push(wins[w].tabs[t]);
}
}
}
if(callback) {
callback(openedTabs);
}
});
}
chrome.tabs.onCreated.addListener(function(tab){
getOpenedTabs(function(openedTabs) {
var length = openedTabs.length;
console.log("Quantity of tabs: " + length );
if (length > 20) {
openedTabs.sort(function(a,b){return a.visitCount - b.visitCount});
var t = openedTabs.shift();
chrome.tabs.remove(t.id);
console.log("The extension closed the " + t.title + " tab");
}
});
});
You don't need to use getAllInWindow(), you can get all tabs with getAll(). Also using in to iterate over an array isn't a good practice.