how to listen for changes to the title element?

Question

In javascript, is there a technique to listen for changes to the title element?

Answer 1

There's not a built-in event. However, you could use setInterval to accomplish this:

var oldTitle = document.title;
window.setInterval(function()
{
    if (document.title !== oldTitle)
    {
        //title has changed - do something
    }
    oldTitle = document.title;
}, 100); //check every 100ms

Answer 2

You can do this with events in most modern browsers (notable exceptions being all versions of Opera and Firefox 2.0 and earlier). In IE you can use the propertychange event of document and in recent Mozilla and WebKit browsers you can use the generic DOMSubtreeModified event. For other browsers, you will have to fall back to polling document.title.

Note that I haven't been able to test this in all browsers, so you should test this carefully before using it.

function titleModified() {
    window.alert("Title modifed");
}

window.onload = function() {
    var titleEl = document.getElementsByTagName("title")[0];
    var docEl = document.documentElement;

    if (docEl && docEl.addEventListener) {
        docEl.addEventListener("DOMSubtreeModified", function(evt) {
            var t = evt.target;
            if (t === titleEl || (t.parentNode && t.parentNode === titleEl)) {
                titleModified();
            }
        }, false);
    } else {
        document.onpropertychange = function() {
            if (window.event.propertyName == "title") {
                titleModified();
            }
        };
    }
};