How do I use an If statement to confirm that an integer has been put into a text field in javascript?
<p>I'm making a simple Fahrenheit to Celcius number conversion function with a button and two text fields as an exercise and I want to make sure my function will stop when someone puts a value in each text field and then tries to execute the function with onclick?</p>

<p>Here is part of the Javascript everything else is ok:</p>

<pre><code>function transfer ()
{
   var fahr= document.form.fahrenheit.value;
   var celc= document.form.celcius.value;

if ( isNaN(celc) || isNaN(fahr))
{
   alert('Please provide a valid number');  
   return;
}     
else if (//what do I put here? == true)
}
   alert('conversion will not calculate correctly with values in both fields');
   return;
}
</code></pre>

<p>I'm really new to programming I hope there is enough info here.</p>
