Change HTML form value with JavaScript before it's submitted

Question

With an external JavaScript file, I'm changing the value of this button below to '5'.

This works, I used console.log to check if the value indeed got changed to '5'.

<form action="getdata.php" method="POST">
  <button type="submit" class="firstHeavyGame button" name='storage' value=''>PRESS THE BUTTON</button>
</form>

Then, when this button is clicked it sends the value to the php site where it processes the data.
BUT, I think then clicking this button, the value gets reset to '' '' (blank). Basic HTML (I'm a newb).
So the php script is not receiving any data.

I checked to see if everything else is working by manually entering the value:

<form action="getdata.php" method="POST">
  <button type="submit" class="firstHeavyGame button" name='storage' value='5'>PRESS THE BUTTON</button>
</form>

This works correctly (gets the number 5 and passes it on to the php file where it gets processed).

Now I know I'm making a newbie mistake but I can't seem to find an answer for my example when doing my research.

Hope you guys can help me out!

Welcome @number42! Can you please give us some additional info, or the code you're using for changing the value of the button? — Brett DeWoody
– Brett DeWoody, Commented Jan 10, 2020 at 13:25
Hi @BrettDeWoody HK KNVB's answer is working. Thank you for the effort! — number42
– number42, Commented Jan 10, 2020 at 13:30

marc_s · Accepted Answer · 2022-05-29 20:49:17Z

2

You may try:

<form action="getdata.php" method="POST" onSubmit="setValue(this)">
   <button type="submit" class="firstHeavyGame button" name='storage' value=''>PRESS THE BUTTON</button>
</form> 
<script>
    function setValue(v) {
         v.storage.value="5";
         return true;
     }
</script>

edited May 29, 2022 at 20:49

marc_s

760k186 gold badges1.4k silver badges1.5k bronze badges

answered Jan 10, 2020 at 13:24

HK KNVB

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