当使用正则表达式包装页面中所有单词的span标记时，正则表达式-Javascript存在问题

// remove duplicates from an array
function unique(arr) {
  for (var i = 0; i < arr.length; i++) {
    for (var j = i + 1; j < arr.length; j++) {
      if (arr[i] == arr[j]) {
        arr.splice(j, 1);
        j--;
      }
    }
  }
  return arr;
}

// Wrap 'span' tags around all words
function add_span(word_array, element_) {
  for (let i = 0; i < word_array.length; i++) {
    // ????????????????Regular expression cannot join \[\]
    var reg_str = "([ \s\t\r\n.?,\"\';:!(){}<>\/]|\xa0|\x20|\u3000| )";
    var reg = new RegExp(reg_str + "(" + word_array[i] + ")" + reg_str, 'g');
    element_ = element_.replace(reg, '$1$2$3');
  }
  return element_;
}

window.onload = function() {
  console.log(document.body.innerText); // all text in body
  // text to word array
  var word_array = document.body.innerText.split(/[ \s\t\r\n.?,\"\';:!()\[\]{}<>\/]|\xa0|\x20|\u3000| /);
  word_array = word_array.filter(e => e != ''); // remove empty values
  word_array = unique(word_array); // remove duplicate values
  console.log(word_array);

  // Wrap 'span' tags around all words
  var text_html = add_span(word_array, document.body.innerHTML);
  document.body.innerHTML = text_html;
  console.log(text_html);
}

span {
  background: #ccc;
}