How to append the string to textarea using javascript -

i want append given string textarea have, want append text in way should typing on texture,because have voice playing in background 6 seconds which says same thing written.

<textarea id='typeable' style='font-size:18px;background:#f8e71c'></textarea>      <script>     function addtext(event) {         document.getelementbyid("typeable").value += "hello welcome new world of javascript"     }     </script> 

how can

count number of characters in sentence, , calculate time each char dividing total time no. of characters , call time interval , run until characters printed.

still can decide time taken print each character , modify per need. please note time taken in milliseconds.

var chars = "hello welcome new world of javascript".split("");  var textarea = document.queryselector('textarea');  var total_time=6000;  var index = 0;  var time_per_char = total_time/chars.length;  var t = setinterval(function(){   textarea.value += chars[index];    index++;    if (index === chars.length){     clearinterval(t);    }  },time_per_char);

<textarea style="width:100%;background:#e1ecf4">    </textarea>