Tag: getElementById

function tekstsize(h) {
  var elem = document.getElementById("main_text");
  elem.style.height = h + 'px';
}

<input type="button" name="wybor" value=" - " onClick="tekstsize(150)">
<input type="button" name="wybor" value=" + " onClick="tekstsize(1000)">
<textarea name="main_text" id="main_text" cols='90' rows='10' wrap='virtual'>