<div>Hello, my name is B<span></span>ob</div>

div {
  width: 147px;
  background: yellow;
}

span {
  width: 0;
  height: 0;
  overflow: hidden;
  position: absolute;
  background: red;
}
span.on {
  width: 3px;
  height: 10px;
}

onclick = function () {
  document.querySelector("span").classList.add("on");
};