HTMLify

const textEl = document.getElementById("text");
const speedEl = document.getElementById("speed");

const text = "We Love Programming!";
let idx = 1;
let speed = 300 / speedEl.value;

writeText();

function writeText() {
  textEl.innerHTML = text.slice(0, idx);
  idx++;

  if (idx > text.length) {
    idx = 1;
  }

  setTimeout(writeText, speed);
}
speedEl.addEventListener("input", (e) => {
  speed = 300 / e.target.value;
});