form-data-set-usv-form.html
<!DOCTYPE html>
<meta charset="utf-8">
<title>This is the form that will be submitted</title>
<form action="form-echo.py" method="post" enctype="text/plain">
<input id="input1" type="text">
<select id="input2">
<option selected>option
</select>
<input id="input3" type="radio" checked>
<input id="input4" type="checkbox" checked>
</form>
<script>
"use strict";
const form = document.querySelector("form");
for (let el of Array.from(form.querySelectorAll("input"))) { // Firefox/Edge support
el.name = el.id + "\uDC01";
el.value = el.id + "\uDC01";
}
const select = document.querySelector("select");
select.name = select.id + "\uDC01";
select.firstElementChild.value = select.id + "\uDC01";
</script>