MutationObserver Too Long Example

MutationObserver-TooLong.js

// target element that we will observe
const target = document.querySelector('div');

// config object
const config = {
  characterData: true,
  characterDataOldValue: true,
  childList: true,
  subtree: true
};

// subscriber function
function subscriber(mutations) {
  mutations.forEach((mutation) => {
    if (mutation.addedNodes.length && mutation.addedNodes[0].length > 5) {
      mutation.target.innerText = 'too long';
    }
  });
}

// instantiating observer
const observer = new MutationObserver(subscriber);

// observing target
observer.observe(target, config);