while (expression){
  Statement(s) to be executed if expression is true
}

<script type="text/javascript">
<!--
var count = 0;
document.write("Starting Loop" + "<br />");
while (count < 10){
 document.write("Current Count : " + count + "<br />");
 count++;
}
document.write("Loop stopped!");
//-->
</script>

Starting Loop
Current Count : 0
Current Count : 1
Current Count : 2
Current Count : 3
Current Count : 4
Current Count : 5
Current Count : 6
Current Count : 7
Current Count : 8
Current Count : 9
Loop stopped! 

do{
  Statement(s) to be executed;
} while (expression);

<script type="text/javascript">
<!--
var count = 0;
document.write("Starting Loop" + "<br />");
do{
 document.write("Current Count : " + count + "<br />");
 count++;
}while (count < 0);
document.write("Loop stopped!");
//-->
</script>

Starting Loop
Current Count : 0
Loop stopped!