What is the best method to determine if a text box is filled or empty?

Question

What is the best method to determine if a text box is filled or empty?

I need to verify whether a text box is populated with a name. If it is empty, an alert message should be shown upon clicking the submit button, and the page should not proceed with submitting the blank value. If there is a value in the text box, then that value should be submitted.

Below is the code I am currently using. When I leave the text box empty and click on the submit button, the alert pops up as expected. However, the form still submits the empty value after dismissing the alert.

<html>
    <head>
        <script type="text/javascript">

            function check()
            {
                if (!frm1.FileName.value)
                {
                    alert ("Please Enter a File Name");
                    return (false);
                }
                return (true);
            }

        </script>
    </head>
    <body>
        <form name="frm1" id="frm1" action="/cgi-bin/page.pl" method="POST">
            <input type="text" name="FileName" id="FileName">       
            <input type="submit" value="send" name="btn_move" id="btn_move" onclick="check()">
        </form>
    </body>
</html>

What could be causing this issue in the code?

javascript dom-events

Answer 1

Answer №1

Make sure to include onclick="return check();"

Answer 2

Make sure to include onclick="return check();"

Answer 3

Answer №2

Here is a simple HTML form validation script:

<html>
    <head>
        <script type="text/javascript">

            function check()
            {
                if (document.getElementById('FileName').value==""
                 || document.getElementById('FileName').value==undefined)
                {
                    alert ("Please Enter a File Name");
                    return false;
                }
                return true;
            }

        </script>
    </head>
    <body>
        <form name="frm1" id="frm1" action="/cgi-bin/page.pl" method="POST">
            <input type="text" name="FileName" id="FileName">       
            <input type="submit" value="send" name="btn_move" id="btn_move" onclick="return check();">
        </form>
    </body>
</html>

Answer 4

Here is a simple HTML form validation script:

<html>
    <head>
        <script type="text/javascript">

            function check()
            {
                if (document.getElementById('FileName').value==""
                 || document.getElementById('FileName').value==undefined)
                {
                    alert ("Please Enter a File Name");
                    return false;
                }
                return true;
            }

        </script>
    </head>
    <body>
        <form name="frm1" id="frm1" action="/cgi-bin/page.pl" method="POST">
            <input type="text" name="FileName" id="FileName">       
            <input type="submit" value="send" name="btn_move" id="btn_move" onclick="return check();">
        </form>
    </body>
</html>

Answer 5

Answer №3

When you use the check function and return false, it's important to remember that you need to also return the value from the event handler itself.

By returning false from the event handler, you are able to prevent the default action (such as submitting a form). Here's an example of how this can be implemented:

onclick="return check();"

If you're looking to learn more about event handling beyond inline event handlers, I recommend checking out the informative introduction to event handlers at quirksmode.org.

A best practice is to perform these checks right before a form is submitted, rather than when the submit button is pressed. One way to do this is by binding the event handler to the submit event of the form. Here's an example using traditional event handlers:

document.getElementById('frm1').onsubmit = function() {
    if (!this.FileName.value) {
        alert ("Please Enter a File Name");
        return false;
    }
};

The benefit of this approach is that the validation will occur for all form submissions, not just when the submit button is clicked (for instance, if the enter key triggers form submission).

Answer 6

When you use the check function and return false, it's important to remember that you need to also return the value from the event handler itself.

By returning false from the event handler, you are able to prevent the default action (such as submitting a form). Here's an example of how this can be implemented:

onclick="return check();"

If you're looking to learn more about event handling beyond inline event handlers, I recommend checking out the informative introduction to event handlers at quirksmode.org.

A best practice is to perform these checks right before a form is submitted, rather than when the submit button is pressed. One way to do this is by binding the event handler to the submit event of the form. Here's an example using traditional event handlers:

document.getElementById('frm1').onsubmit = function() {
    if (!this.FileName.value) {
        alert ("Please Enter a File Name");
        return false;
    }
};

The benefit of this approach is that the validation will occur for all form submissions, not just when the submit button is clicked (for instance, if the enter key triggers form submission).

What is the best method to determine if a text box is filled or empty?

Answer №1

Answer №2

Answer №3

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