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StevenOliver

is this a concat error?

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This hardcoded "999" works fine:
function changeAmount(a){
document.form1.sku999.value="44";
}

But since the number is a php variable, I need this to work. It does not work:
function changeAmount(a){
document.form1.'sku'+a.value="44";
}

In the html below, I "hardcoded" the php variable below to "999" just to try and make the simple javascript above to work.... but it doesn't.

<input onClick="changeAmount('999');" type="button">
<input type="text" name="sku999">

I've spent days trying to learn javascript concatenation, but even this doesn't work:

function changeAmount(a){
var conc = 'sku'+a;
document.form1.conc.value="44";
}

If you would please let me know what I've done wrong. Thank you.

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I don't see any PHP in there. I do see Javascript though. Probably means this question will do better in the Javascript forum.

 

document.form1.sku999.value="44";

sku999 is a name. It is not a variable. You cannot stick a variable in there because Javascript is only going to look at its name.

document.form1.'sku'+a.value="44";

I don't know why you think you can just stick a string in there. There are rules to how this kind of stuff works. Follow the rules.

document.form1.conc.value="44";

Better except that "conc" is a variable, and like I said earlier, Javascript will only look at the name. And form1 doesn't have a "conc".

 

Fortunately there is a way to access an object member using the value of a variable or expression. Square brackets. Just like arrays.

document.form1['sku'+a].value="44";

 

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Try accessing via id

<!DOCTYPE>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Sample</title>
<script type="text/javascript">
    
    function changeAmount(a)
    {
        var sku = document.getElementById("sku"+a)
        sku.value = 44
    }
    
</script>
</head>
<body>

SKU 999 : <input name='sku999' id='sku999' value = ''><br>
<button id='mybtn' onclick='changeAmount(999)'>Set value</button>
</body>
</html>

 

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requinix, thank you! In days of searching, I never found the brackets suggestion.
Also, I'll give more attention to the correct forum topic (or, at least I should have put <?php echo..." on top LOL )

Barand, thank you!
The html is a result of a PHP loop through 100+ mySQL records, and since I already have "<textarea name=sku<?=$number?>...." at least 100+ times, I thought it would "bog down the html page size" if I additionally added id="sku<?=$number?>" to all 100+ textareas. (I still think in terms of the 1990's browsers where you had to keep an eye on each extra unnecessary byte...

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10 minutes ago, StevenOliver said:

since I already have "<textarea name=sku<?=$number?>...." at least 100+ times

That form is going to be one major headache when it's posted. Use array syntax when naming your fields then processing them is just a loop,

<textarea name='sku[$number]' >

 

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It's a loop like this:

while ($sku = $query->fetch_assoc()) { // a hundred results
echo '<textarea name="'.$sku["product_name"].' ..... etc.

And that produces a huge amount of html.

I meant that if I added an id tag to that, it would almost double the amount of html sent to the browser:
echo '<textarea name="'.$sku["product_name"].' id="'.$sku["product_name"].'"... etc. //

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