html button click only once

<script>
function doSomething () {
  // Remove onclick
  var element = document.getElementById("myDiv");
  element.onclick = "";

  // Do your processing here
  alert("Something is done!");

  // Re-enable after processing if you want
  // element.onclick = doSomething;
}
</script>

<div id="myDiv" onclick="doSomething()">
  Click Here To Do Something
</div>