Firefox XPCOM setTimeout problem

I am writing a simple firefox extensions which 开发者_开发百科crawls a bunch of urls and extracts certain fields (all urls that are crawled will be loaded in the user's tab).

The problem I am facing is in the part actually visits the URL and loads the page. I want each page to be loaded at a fixed timer period. eg, Each site to be visited every 5 seconds.

I tried the two methods listed here http://groups.google.com/group/mozilla.dev.extensions/browse_thread/thread/de47c3949542b759 but to no avail. Using both Components.classes["@mozilla.org/appshell/appShellService;1"] and also nsITimer. The while loops executes immediately and the pages are loaded later (after about 5 seconds in quick succession)

 function startCrawl()
    {
        while(urlq.length>0)
        {
            var currentUrl = urlq.shift();
            urlhash[currentUrl]=1;

            if(currentUrl!=undefined)
            {
                setTimeout(gotoURL,5000,currentUrl);
            }

        }
            start=0;
            alert('crawl stopped');

            for(var k in foundData)
            {
                alert('found: ' + k);
            }           

    }

    function gotoURL(gUrl)
    {
        mainWindow.content.wrappedJSObject.location=gUrl;
        extractContent();

    }

How do I implement the timer function that calls gotoURL every 5 seconds correctly? Thanks!

Well, setTimeout is executed asynchronously. The loop does not wait until the function is called. You have to change the strategy (if I understood you correctly).

For example you could trigger the next setTimeout after you extracted the information:

function startCrawl() {
    function next() {
        var currentUrl = urlq.shift();
        if(currentUrl) {
            setTimeout(gotoURL,5000,currentUrl, next);
        }
    }
    next();    
}

function gotoURL(gUrl, next) {
    mainWindow.content.wrappedJSObject.location=gUrl;
    extractContent();
    next();
}

And yes, it is better to use nsITimer.