How to find which is the biggest value?

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	function func()
	{
              var divs = document.getElementsByTagName('div');
              for(var i=0; i<divs.length; i++)
              {
                 if(divs[i].className.indexOf = 'some-class-name')
                 {
                      var heights = divs[i].offsetHeight;

                      /* How to find which is 
                          the biggest value for 'var heights' ? */
                 }
              }
	}
	window.onload = func;
</script>

<script type="text/javascript">
	function func()
	{
              var maxVal=-1;
              var divs = document.getElementsByTagName('div');
              for(var i=0; i<divs.length; i++)
              {
                 if(divs[i].className.indexOf = 'some-class-name')
                 {
                      var heights = divs[i].offsetHeight;
                      if (heights >  maxVal) {
                            maxVal = heights;
                      }
                 }
              }
              if (maxVal ==-1) {
                  alert('For some reaon there is no max value.')
              } else {
                  alert('maxVal = ' + maxVal )
              }
	}
	window.onload = func;
</script>