GetTextContent.js

var observer = new MutationObserver(function (mutations) {
  mutations.forEach(function (mutation) {
    if (mutation.target.className === "ms-List-cell" || mutation.target.className === "ms-List-surface") {
      var customBody = document.getElementsByClassName('customBody');

      for (var i = 0, len = customBody.length | 0; i < len; i = i + 1 | 0) {
        var ret;
        customBody[i].innerHTML = customBody[i].textContent;
        ret = truncate(customBody[i].textContent, 100);
        customBody[i].innerText = ret;
      }
    }
  });
});
var config = {
  subtree: true,
  childList: true
};
observer.observe(document.documentElement, config);

function truncate(str, len) {
  return str.length <= len ? str : str.substr(0, len) + "...";
}