Chrome extension to replace text on webpage works only after manually refreshing webpage sometimes

Question

I am developing a chrome extension to replace specific texts on webpage. For some websites, it works only after refreshing webpages manually with F5. For example, when I open http://www.iciba.com/ and input Google and press Enter, all Google texts in results are not replaced. But after I press F5 to refresh page manually, all texts are replaced.

manifest.json:

{
    "name": "My Extension",
    "version": "0.1.0",
    "description": "An extension that replaces texts on webpages",
    "manifest_version": 2,
    "permissions": [
        "tabs",
        "<all_urls>"
    ],
    "content_scripts": [{
        "matches": [
            "http://*/*",
            "https://*/*"
        ],
        "js": [
            "replacetxt.js"
        ],
        "run_at": "document_end",
        "all_frames": true
    }]
}

replacetxt.js:

function isExcluded(elm) {
  if (elm.tagName == "STYLE") {
    return true;
  }
  if (elm.tagName == "SCRIPT") {
    return true;
  }
  if (elm.tagName == "NOSCRIPT") {
    return true;
  }
  if (elm.tagName == "IFRAME") {
    return true;
  }
  if (elm.tagName == "OBJECT") {
    return true;
  }
  return false
}

function traverse(elm) {
  if (elm.nodeType == Node.ELEMENT_NODE || elm.nodeType == Node.DOCUMENT_NODE) {

    // exclude elements with invisible text nodes
    if (isExcluded(elm)) {
      return
    }

    for (var i=0; i < elm.childNodes.length; i++) {
      // recursively call to traverse
      traverse(elm.childNodes[i]);
    }

  }

  if (elm.nodeType == Node.TEXT_NODE) {

    // exclude text node consisting of only spaces
    if (elm.nodeValue.trim() == "") {
      return
    }

    // elm.nodeValue here is visible text we need.
    console.log(elm.nodeValue);
    elm.nodeValue = elm.nodeValue.replace("Google", "***");
  }
}

traverse(document);

Here are working codes following @wOxxOm's advice

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

// Callback function to execute when mutations are observed
const callback = function(mutationsList, observer) {
    // Use traditional 'for loops' for IE 11
    for(const mutation of mutationsList) {
        traverse(mutation.target);
    }
};

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

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

Answer 1

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

// Callback function to execute when mutations are observed
const callback = function(mutationsList, observer) {
    // Use traditional 'for loops' for IE 11
    for(const mutation of mutationsList) {
        traverse(mutation.target);
    }
};

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

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