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Wait for key element

A utility function, for Greasemonkey scripts, that detects and handles dynamic content.

Tento skript by nemal byť nainštalovaný priamo. Je to knižnica pre ďalšie skripty, ktorú by mali používať cez meta príkaz // @require https://update.greasyfork.org/scripts/482702/1299083/Wait%20for%20key%20element.js 

// ==UserScript==
// @name          Wait for key elements
// @namespace     http://tampermonkey.net/
// @version       0.1
// @description   A utility function, for Greasemonkey scripts, that detects and handles dynamic content.
// @author        https://github.com/cgriebel
// @grant         none
// @include       *
// ==/UserScript==

/*--- waitForKeyElements():  
    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().");
        }
*/
function waitForKeyElements(
  selectorTxt,    /* Required: The 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. */
  waitOnce,      /* 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. */
) {
  const dataAttr = 'data-wait-for-elements-found';
  var targetNodes, targetsFound;

  if (typeof iframeSelector == "undefined") {
    var nodes = document.querySelectorAll(selectorTxt);
    targetNodes = nodes ? [...nodes] : null;
  }
  else {
    // TODO: CG - test iframes, I currently have no use for this
    // targetNodes = $(iframeSelector).contents()
    //   .find(selectorTxt);
  }

  if (targetNodes && targetNodes.length > 0) {
    targetsFound = true;
    /*--- Found target node(s).  Go through each and act if they
        are new.
    */
    targetNodes.forEach((node) => {
      if (!node.getAttribute(dataAttr)) {
        //--- Call the payload function.
        var cancelFound = actionFunction(node);
        if (cancelFound) {
          targetsFound = false;
        }
        else {
          node.setAttribute(dataAttr, true);
        }
      }
    })
  }
  else {
    targetsFound = 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 (targetsFound && waitOnce && 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,
          waitOnce,
          iframeSelector
        );
      },
        300
      );
      controlObj[controlKey] = timeControl;
    }
  }
  waitForKeyElements.controlObj = controlObj;
}