java script to check is value is not empty

I know nothing about java script other than its client side.  I want to modify a form so that if a user enters null values it highlights the form that wasnt entered and states something like what yahoo do see below

https://edit.europe.yahoo.com/registration?.intl=ie&.pd=ym_ver%253D0%2526c%253D%2526ivt%253D%2526sg%253D&new=1&.done=http%3A//mail.yahoo.com&.src=ym&.v=0&.u=amrr5ep6o6e9k&partner=&.partner=&pkg=&stepid=&.p=&promo=&.last=
enigma1234567890Asked:
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pnpatneConnect With a Mentor Commented:
This is what you are looking for:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
      <script>
            function checkIfEmpty()
            {
                  if( document.getElementById("text1").value.length == 0)
                  {
                        document.getElementById('error').style.display="block";
                  }
            }
      </script>
      <style type="text/css">
            .text1
            {
                  color:red;
            }
      </style>
</HEAD>

<BODY>
      <p>
      Text1 :  <input type="text" id="text1"/>
      <label id="error" class="text1" style="display:none;">Text1 is required.</label>
      </p>
<br>
      <input type="button" value="submit" onclick="checkIfEmpty()"/>
</BODY>
</HTML>
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Gurvinder Pal SinghCommented:
try this
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
	<script>
		function checkIfEmpty()
		{
			if( document.getElementById("text1").value.length == 0)
			{
				alert("enter something here");
			}
		}
	</script>
</HEAD>

<BODY>
	<input type="text" id="text1"/>

	<input type="button" value="submit" onclick="checkIfEmpty()"/>
</BODY>
</HTML>

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0
 
foobarrConnect With a Mentor Commented:
to slightly modify the above code

if (document.getElementById("text") == null)
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