How to translate PHP to js?

Question

PHP

It is necessary to translate PHP into JS, because it is not possible to pull out $data, $signature in value input in WordPress in ways possible in PHP (please do not write about shortcodes, plugins, widgets, I tried everything, nothing works), but it is necessary that to send a request.
At the same time, it is necessary that $amount be read and passed to processing even before submitting the form, so $POST_['amount'] is not very suitable, but I wanted to solve this issue after.
I am by no means an expert in JS. Undertook to translate, but a jamb pops up, after a jamb, please help.

form method="POST" action="/action.php">
<input type="hidden" id ="data" name="data" value="<?php echo $data; ?>"/>
<input type="hidden" id ="signature" name="signature" value="<?php echo $signature; ?>"/>
<input type="number" id ="amount" name="amount" value="10"/>
<input type="image" src="/button.png"/>

$order_id = date("d/m/Y-H:i:s");
$amount = $_POST['amount'];
$private_key = "i00000000";
$public_key = "i00000000";
$arr = array('version'     => 3,
             'public_key'  => $public_key,
              'amount'      => $amount,
              'action'      => 'pay',
              'currency'    => 'UAH',
              'description' => 'Donate',
              'order_id'    => $order_id,
);
$data = base64_encode( json_encode($arr));
$signature = base64_encode( sha1($private_key .$data .$private_key, 1 ));

Answer 1

Or alternatively how to convert $data to text value?
Now the shortcode displays as it says $data, not the value of the variable...

function data_text_shortcode() {
    return '$data';
}
add_shortcode('datashortcode', 'data_text_shortcode');