i want  if div size width:100%;height:100% then also canvas size is width:100%;height:100%  (not using pix)

<div id=”parent” style=”position:absolute;background-size:100% 100%;background-color:blue;width:100%;height:100%”>
        <canvas id=”theCanvas” style=”background-color: red;”>
        </canvas>
    </div>

<script>
$(document).ready(function() {
  var canvas = document.getElementById(“theCanvas”);
  canvas.width = $(“#parent”).width();
  canvas.height = $(“#parent”).height();
  canvas.position = $(“#parent”).position();
  canvas.background-size = $(“#parent”).background-size();
});
</script>