Javascript: What is wrong with this conditional?

Question

I'm working on a Chrome extension an I've hit a wall.

function isInQueue(id) {
    chrome.extension.sendRequest({getQueueItems: 1}, function(response) {
        var items = response.items;
        if (items) {
            for (var i = 0; i < items.length; i++) {
                if ((items[i].id == id) == true) return true;
            }
            return false;
        } else { return false; }
    });
}

The request returns 'items' which is an array of objects. I am trying to see if another item outside of the queue already exists inside the queue. For example, there is an item on the outside with an id equal to '198677'. I know I already have an exact copy of that same item in my queue with the exact same id, '198677', however, when I test the two for equality (items[i].id == id) == true , it returns false. I have checked the typeof both and they are both strings. I have tried using === and that hasn't worked. I tried adding zero to each of them to turn them into integers and that made the function return true when it was actually true, however, when I tested for true if (isInQueue(id) == true) the conditional returned false.

This is all very confusing and frustrating for me. They're both strings, why doesn't it work?

Help is very much appreciated.

Answer 1

The problem is chrome.extension.sendRequest is asynchronous - it returns immediately, but the callback function you provide to it will only be called once the request has completed.

The usual way to handle something like this is to pass a callback to your isInQueue method; the callback is called when the asynch operation is completed with the result.

function isInQueue(id, callback) {
    chrome.extension.sendRequest({getQueueItems: 1}, function(response) {
        var result = false;
        var items = response.items;
        if (items) {
            for (var i = 0; i < items.length; i++) {
                if ((items[i].id == id) == true) {
                  result = true;
                  break;
                }
            }
        }
        callback(result);
    });
}

Answer 2

I figured it out:

function isInQueue(id) {
    var result = false;
    var queue = localStorage["queue_rss"];
    if (queue != undefined) {
        var items = JSON.parse(queue).items;
        if (items) {
            for (var i = 0; i < items.length; i++) {
                if ((items[i].id == id) == true) {
                  result = true;
                  break;
                }
            }
        }
    }
    return result;
}

I should have done it that way in the first place. Thanks guys. :D