typewriter.js

var span = document.querySelector(".typewriter span");
var textArr = span.getAttribute("data-text").split(", ");
var maxTextIndex = textArr.length;

var sPerChar = 0.15;
var sBetweenWord = 1.5;
var textIndex = 0;

typing(textIndex, textArr[textIndex]);

function typing(textIndex, text) {
  var charIndex = 0;
  var maxCharIndex = text.length - 1;

  var typeInterval = setInterval(function () {
    span.innerHTML += text[charIndex];
    if (charIndex == maxCharIndex) {
      clearInterval(typeInterval);
      setTimeout(function () {
        deleting(textIndex, text);
      }, sBetweenWord * 1000);
    } else {
      charIndex += 1;
    }
  }, sPerChar * 1000);
}

function deleting(textIndex, text) {
  var minCharIndex = 0;
  var charIndex = text.length - 1;

  var typeInterval = setInterval(function () {
    span.innerHTML = text.substr(0, charIndex);
    if (charIndex == minCharIndex) {
      clearInterval(typeInterval);
      textIndex + 1 == maxTextIndex ? (textIndex = 0) : (textIndex += 1);
      setTimeout(function () {
        typing(textIndex, textArr[textIndex]);
      }, sBetweenWord * 1000);
    } else {
      charIndex -= 1;
    }
  }, sPerChar * 1000);
}