js style dynamically sets table height_javascript skills

function com_onresize(){

var contentsHeight = document.body.clientHeight;
var buttonsHeight = document.getElementById( "buttons" ).offsetHeight;
var head1Height = document.getElementById( "head1" ).offsetHeight;
var head2Height = document.getElementById( "head2" ).offsetHeight;

var t1 = document.getElementById( "TableContainer1" ).style.height;
var t2 = document.getElementById( "TableContainer2" ).style.height;

//alert(document.getElementById( "TableContainer1" ).style.height);
var h = contentsHeight - buttonsHeight - head1Height - head2Height - 13;
if(h < 110){
return;
}
document.getElementById( "TableContainer1" ).style.height = h/2 + 'px';
document.getElementById( "TableContainer2" ).style.height = h/2 + 'px';
}
function com_sbs_pagesize(){
var screenHeight = window.screen.height;
  var availHeight = window.screen.availHeight;
  //alert(document.getElementById( "TableContainer1" ).children[0].rows.length);
  var index = document.getElementById( "TableContainer1" ).children[0].rows.length
  var buttonsHeight = document.getElementById( "buttons" ).offsetHeight;
var head1Height = document.getElementById( "head1" ).offsetHeight;
var head2Height = document.getElementById( "head2" ).offsetHeight;

  var mainH = buttonsHeight + head1Height +head2Height + 13;
  //20:scroll 35:title 25:tr
  while ((availHeight-mainH) < (20 + 35 + 25*index)*2)
{
 index = index - 1;
}
var tableHeight = 20 + 35 + 25*index;
  document.getElementById( "TableContainer1" ).style.height = tableHeight + 'px';
  document.getElementById( "TableContainer2" ).style.height = tableHeight + 'px';
  window.resizeTo(document.body.offsetWidth,mainH + tableHeight*2);
}