How can define / use a dynamic variable in JS?

Asked Jul 23 '19 at 08:39

Active Jul 23 '19 at 08:43

Viewed 23 times

I'm currently defining multiple global JS vars in a PHP foreach within a div this way:

<script>
    var signaturePad<?= $i ?>;
</script>

Output:

var signaturePadYWduZFlQVm9xS1dhNDJYYU1ZdCtWUT09;

I need to do this because I later need to get some content from the global var depending on the shown div.

Now I've the problem that I don't know how I can use the generated variable in JS. I've tried it this way but this can't work:

var targetId = jQuery(this).attr('data-target-id'); //The id after signaturePad....
signaturePad + targetId = new SignaturePad();

Later I need to get for example a signature from the object:

signaturePad + targetId.toDataURL('image/png')

Any idea how I can deal with this?

edited Jul 23 '19 at 08:43

asked Jul 23 '19 at 08:39

Mr. Jo

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Use an object (or array) instead – CertainPerformance Jul 23 '19 at 08:41
Can you give me an example? :) I've never done this before.. – Mr. Jo Jul 23 '19 at 08:42
See the linked canonical. – CertainPerformance Jul 23 '19 at 08:42
@CertainPerformance Still not logic to me how I can use this correctly :/ – Mr. Jo Jul 23 '19 at 08:47
And the answer returns just a number but concats nothing (in the duplicate) – Mr. Jo Jul 23 '19 at 08:55
Eg `const signaturePad = { YWduZFlQVm9xS1dhNDJYYU1ZdCtWUT09: }` and then use plain bracket notation to assign or look up the value – CertainPerformance Jul 23 '19 at 08:59
You mean: signaturePad = { targetId: new SignaturePad(signaturePadCanvas) }; ??? – Mr. Jo Jul 23 '19 at 09:15
No, that would have only a single property, `targetId`, not the (dynamic) property `YWduZFlQVm9xS1dhNDJYYU1ZdCtWUT09` that you're looking for – CertainPerformance Jul 23 '19 at 09:16
But target id is defined dynamically. See above. The target ID is a unique ID of the div where the signature pad is inside. – Mr. Jo Jul 23 '19 at 09:17
Exactly, so you have to use bracket notation to assign or look up the property – CertainPerformance Jul 23 '19 at 09:18
I don't get it anymore – Mr. Jo Jul 23 '19 at 09:19
@CertainPerformance Can you please give me a short example with my implementation, so that I can understand it? – Mr. Jo Jul 23 '19 at 09:42
Define the pads with `const signaturePad = { YWduZFlQVm9xS1dhNDJYYU1ZdCtWUT09: }`. If there's no initial value, just use an empty object. Then retrieve / assign to properties of the object. eg `signaturePad[foo] = 'bar'` – CertainPerformance Jul 23 '19 at 09:44
In my main js I now did: let signaturePad; in PHP this: but this generates an error: Uncaught SyntaxError: Unexpected token ] – Mr. Jo Jul 23 '19 at 09:54
Since it looks like you're not assigning values to the object initially, leave that out entirely - just create an empty object – CertainPerformance Jul 23 '19 at 09:56
I'll re-write my question above with the new implementation, ok? – Mr. Jo Jul 23 '19 at 09:57

How can define / use a dynamic variable in JS?

0 Answers0