addChildListListener.jsx

// listen for creation of a modal
$(document).on('click', '.modal-with-react', function() {
  addChildListListener('modal-holder')
})

export function addChildListListener(elementId){
  // Select the node that will be observed for mutations
  const targetNode = document.getElementById(elementId)

  // Options for the observer (which mutations to observe)
  const config = { childList: true }

  // Callback function to execute when mutations are observed
  const callback = function(mutationsList, observer) {
    for(let mutation of mutationsList) {
      if (mutation.type === 'childList') {
        insertDatePickers()

        // stop observing
        observer.disconnect();
      }
    }
  };

  // Create an observer instance linked to the callback function
  const observer = new MutationObserver(callback)

  // Start observing the target node for configured mutations
  observer.observe(targetNode, config)
}