Javascript Natural Gas Units

<h2>
Natural Gas Unit Conversion Tool
</h2>
<script language="JAVASCRIPT">

<!-- hide this from old browsers


function clearForm(form){
   form.dTh.value   ="";
   form.BCf.value   ="";
   form.MCf.value   ="";
   form.MMBtu.value ="";
   form.Nymex.value ="";
}

function addCommas(nStr)
{
  nStr += '';
  x = nStr.split('.');
  x1 = x[0];
  x2 = x.length > 1 ? '.' + x[1] : '';
  var rgx = /(\d+)(\d{3})/;
  while (rgx.test(x1)) {
    x1 = x1.replace(rgx, '$1' + ',' + '$2');
  }
  return x1 + x2;
}
function evalForm(form) {
   var dTh    = parseFloat(form.dTh.value);
   var BCf    = parseFloat(form.BCf.value);
   var MCf    = parseFloat(form.MCf.value);
   var MMBtu  = parseFloat(form.MMBtu.value);
   var Nymex  = parseFloat(form.Nymex.value);
   if (isNaN(dTh))   dbool=0; else dbool=1;
   if (isNaN(BCf))   bbool=0; else bbool=1;
   if (isNaN(MCf))   cbool=0; else cbool=1;
   if (isNaN(MMBtu)) mbool=0; else mbool=1;
   if (isNaN(Nymex)) nbool=0; else nbool=1;
   allVals=dbool+bbool+cbool+mbool+nbool;

   if (allVals!=1){
      alert("\nPlease enter one value\n");
      clearForm(form);
      return false;
   }
   if (mbool) dTh=MMBtu;
   if (bbool) dTh=BCf*1000000;
   if (cbool) dTh=MCf;
   if (nbool) dTh=Nymex*10000;
   form.dTh.value=dTh;
   return true;
}

function computeForm(form) {
   if (evalForm(form)) {
      
      MMBtuValue=form.dTh.value;
      BCfValue=form.dTh.value/1000000;
      MCfValue=form.dTh.value;
      form.dTh.value=addCommas(form.dTh.value);
      form.BCf.value=addCommas(BCfValue);
      form.MCf.value=addCommas(MCfValue);
      form.MMBtu.value=addCommas(MMBtuValue);
      Contracts=addCommas(MMBtuValue/10000);
      form.Nymex.value=addCommas(Contracts);
   }
   form.dTh.value = form.dTh.value;
   return;
}
 // -- done hiding from old browsers -->

</script>





<center>

<hr size="10"/>
<a name="Calc">


Enter a number in one of the boxes<br/>
in the form below and press the "Convert" button<br/>

<form>
<table border="1">
<tr>
<td><div align="CENTER">dTh-DekaTherms</div></td>

<td><div align="CENTER">BCf-Billion Cubic Feet*</div></td>

<td><div align="CENTER">MCf-Thousand Cubic Feet*</div></td>
<td><div align="CENTER">MMBtu-Million Btu</div></td>
<td><div align="CENTER">NYMEX Contracts</div></td>
</tr>

<tr>
<td><input name="dTh" type="TEXT"/></td>
<td><input name="BCf" type="TEXT"/></td>
<td><input name="MCf" type="TEXT"/></td>
<td><input name="MMBtu" type="TEXT"/></td>

<td><input name="Nymex" type="TEXT"/></td>

</tr></table>

<p>

<input value="Convert" onclick="computeForm(this.form)" type="button"/>
<input value="Reset" onclick="clearForm(this.form)" type="button"/>
</p></form>

</a>
<hr/>
</center>

*BCf and MCf volume measurements vary with temperature and pressure (i.e. location
and time of the year). 
<br/>The conversion of 1BCf=1,000,000 MMBtu is accepted by the NYMEX Conversion Table.
<p>

<hr size="10"/>
</p>