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Editorial Team
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Asked: 2026-06-07T11:24:47+00:00

I have been trying different methods and looking in many different places, and it

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I have been trying different methods and looking in many different places, and it really looks like the following code should work. I am stumped as to why it isn’t… I am a novice to html and JavaScript, so I’m guessing I keep overlooking something I did wrong? If so, hopefully someone can point it out. 

<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
<!--
    function validateUsername() {
        if (document.getElementById("username") == "") {
           document.registrationform.username.style.background = 'Yellow';
        }
    }
//-->
</script>
</head>
<body>

<form name="registrationform" id="registrationform" method="post" action="register.php"> 

    <div class="formlabel">*Username:</div>
    <div class="formfield"><input type="text" name="username" id="username" size="30" onblur="validateUsername()"/></div>
    <div style="float:left;">
        <input type="submit" value="Submit" />
    </div>
</form>
</body>
</html>

When I leave it blank and click out of it, it does not change color like I’d like. Why?

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1 Answer

  1. Editorial Team
    document.getElementById("username")

    should be

    document.getElementById("username").value

    That should get you started. However, your implementation won’t catch cases where the user has entered a space (” “) into the textbox. For that, you’ll use the trim function to get rid of the spaces:

    // Remove spaces at front/back of value in textbox
document.getElementById("username").value.trim();
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