waitForKeyElements.js

/**
 * Source: https://gist.github.com/BrockA/2625891
 * Use this in your TamperMonkey script header:
// @require https://cdn.jsdelivr.net/npm/jquery@3/dist/jquery.min.js
// @require https://raw.githubusercontent.com/moderntribe/tampermonkey-scripts/master/waitForKeyElements.js
 */

/*--- waitForKeyElements():  A utility function, for Greasemonkey scripts,
    that detects and handles AJAXed content.

    Usage example:

        waitForKeyElements (
            "div.comments"
            , 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
                        element.
                    */
	bWaitOnce,      /* Optional: If false, will continue to scan for
                        new elements even after the first match is
                        found.
                    */
	iframeSelector  /* Optional: If set, identifies the iframe to
                        search.
                    */
) {
	var targetNodes, btargetsFound;

	if (typeof iframeSelector == "undefined")
		targetNodes     = jQuery(selectorTxt);
	else
		targetNodes     = jQuery(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        = jQuery(this);
			var alreadyFound = jThis.data ('alreadyFound')  ||  false;

			if (!alreadyFound) {
				//--- Call the payload function.
				var cancelFound     = actionFunction (jThis);
				if (cancelFound)
					btargetsFound   = false;
				else
					jThis.data ('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,
						actionFunction,
						bWaitOnce,
						iframeSelector
					);
				},
				300
			);
			controlObj [controlKey] = timeControl;
		}
	}
	waitForKeyElements.controlObj   = controlObj;
}