JSFiddle - React, Tailwind, and code Playground

HTML

<div style="margin-bottom:30px;">Торопись! Цена растет каждую секунду!</div>
<div style="float:left;">12 900,</div>
<div style="float:left;"id="Nnumber"class="price"></div>
<div style="float:left;">&nbsp;руб.</div>
<br /><br />
<input type="submit" value="Стоп">

JavaScript

var My_number=1000;

function growing(b){
  b=1;
  return b;
}
  setInterval(function () {
      My_number=Math.floor(My_number)
      My_number+=growing(My_number);
      document.getElementById('Nnumber').innerHTML=My_number;
  }, 10)