A code to repeat my function / keep displaying the text in javascript

I would like to display the text in the browser again and again in a new line every time, however there is only the first line of text appearing. How this code should be corrected? Besides, I know that setinterval() is to repeat a function, I’d like to ask how can it be used in this code? Thank you very much!

var text = document.getElementById('text');
text.innerText = create_random_string(20);


function create_random_string(string_length){
  var random_string = '';
  var characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  for (var i, i = 0; i < string_length; i++) {
     random_string += characters.charAt(Math.floor(Math.random() * characters.length));
  }
  return random_string; 
}

document.write (
  create_random_string(20) + "<br>",
  create_random_string(20) + "<br>",
  create_random_string(20) + "<br>",
  create_random_string(20) + "<br>",
);