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yukio / waitForKeyElements

// ==UserScript==
// @name         waitForKeyElements
// @description  A utility function for Tampermonkey scripts that detects and handles AJAXed content.
// @license MIT
// ==/UserScript==
/* global $ */

/*--- waitForKeyElements():  A utility function for Tampermonkey 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 = $(selectorTxt);
  else
    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 = 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;
}