Preview:
var getLi = document.querySelectorAll('.main-header__nav .hs-menu-wrapper>ul>li>a');
for (var i = 0; i < getLi.length; i++) {
  var className = getLi[i].innerText;
  var addClassName = className.replace(/\s+/g, "_");
  if (addClassName.length != 0) {
    getLi[i].parentNode.classList.add(addClassName.toLowerCase());
  }
}
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