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A utility function, for Greasemonkey scripts, that detects and handles AJAXed content.
/*--- waitForKeyElements(): A utility function, for Greasemonkey scripts,
that detects and handles AJAXed content.
Usage example:
waitForKeyElements (
, commentCallbackFunction
//--- Page-specific function to do what we want when the node is found.
function commentCallbackFunction (jNode) {
jNode.text ("This comment changed by waitForKeyElements().");
IMPORTANT: This function requires your script to have loaded jQuery.
function waitForKeyElements (
selectorTxt, /* Required: The jQuery selector string that
specifies the desired element(s).
actionFunction, /* Required: The code to run when elements are
found. It is passed a jNode to the matched
bWaitOnce, /* Optional: If false, will continue to scan for
new elements even after the first match is
iframeSelector /* Optional: If set, identifies the iframe to
) {
var targetNodes, btargetsFound;
if (typeof iframeSelector == "undefined")
targetNodes = $(selectorTxt);
targetNodes = $(iframeSelector).contents ()
.find (selectorTxt);
if (targetNodes && targetNodes.length > 0) {
btargetsFound = true;
/*--- Found target node(s). Go through each and act if they
are new.
targetNodes.each ( function () {
var jThis = $(this);
var alreadyFound = ('alreadyFound') || false;
if (!alreadyFound) {
//--- Call the payload function.
var cancelFound = actionFunction (jThis);
if (cancelFound)
btargetsFound = false;
else ('alreadyFound', true);
} );
else {
btargetsFound = false;
//--- Get the timer-control variable for this selector.
var controlObj = waitForKeyElements.controlObj || {};
var controlKey = selectorTxt.replace (/[^\w]/g, "_");
var timeControl = controlObj [controlKey];
//--- Now set or clear the timer as appropriate.
if (btargetsFound && bWaitOnce && timeControl) {
//--- The only condition where we need to clear the timer.
clearInterval (timeControl);
delete controlObj [controlKey]
else {
//--- Set a timer, if needed.
if ( ! timeControl) {
timeControl = setInterval ( function () {
waitForKeyElements ( selectorTxt,
controlObj [controlKey] = timeControl;
waitForKeyElements.controlObj = controlObj;

@BrockA : could we please get this under a BSD or Apache 2.0, or some other compatible license? We'd like to include it in which is apache 2.0.


(also, either way, deep gratitude for writing it!)


Something's wrong with current Firefox, the script just stops on targetNodes.each(). Still works on SeaMonkey or older Firefox, so it's not just me or the page I'm working with, or is it?

What I did was:

-        targetNodes.each ( function () {
-            var jThis        = $(this);
+        for (var i = 0; i < targetNodes.length; i++) {
+            var jThis        = $(targetNodes[i]);

And looks like it works, but I'm not sure if I'm not making some type-casting crime or whatever ;)


It fails to work when other javascript framework use $() as alias. So it's better to use jQuery() explicitly.
You can get update from my fork


Unless you need to support really ancient browsers, use MutationObserver instead.

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