获取添加的 DOM 节点的 className (mutationObserver)

我正在编写一个简单的用户脚本，如果 Facebook 帖子包含特定的单词列表，它将自动隐藏该帖子。核心功能有效，但我的MutationObserver似乎没有读过className of mutation.addedNodes适当地。我循环遍历mutation.addedNodes并检查这些元素是否具有该类userContentWrapper，但该测试的结果始终为 false — 即使该元素确实具有该类。

var startObserver = function() {        
    var observer = new MutationObserver(function(mutations) {        
        mutations.forEach(function(mutation) {            
            var added = mutation.addedNodes;            
            for (var i = 0; i < added.length; i++) {                
                if (/\buserContentWrapper\b/.test(added[i].className)) {
                    processFilter(added[i]);
                }
            }
        });        
    });    
    var obj = {childList: true, subtree: true, attributes: true};
    observer.observe(document.documentElement, obj);
};

我只能假设观察者在所有属性完全形成之前正在分析添加的节点。如何让观察者等待处理节点直到它完全完成？还是我没理解问题？

提前致谢...

一些添加的节点是容器，因此您应该检查它们的内部：

const observer = new MutationObserver(onMutation);
observer.observe(document, {
  childList: true,
  subtree: true,
});

function onMutation(mutations) {
  const found = [];
  for (const { addedNodes } of mutations) {
    for (const node of addedNodes) {
      if (!node.tagName) continue; // not an element
      if (node.classList.contains('userContentWrapper')) {
        found.push(node);
      } else if (node.firstElementChild) {
        found.push(...node.getElementsByClassName('userContentWrapper'));
      }
    }
  }
  found.forEach(processFilter);
}

MutationObserver callback is executed as a microtask that blocks DOM and JS engine so try to make it fast, especially if it runs on a complex site such as facebook that generates lots of DOM mutations. This can be tested in devtools (F12 key) profiler/timeline panels.