JSFiddle - React, Tailwind, and code Playground

HTML

<div class='form-modelo'>
    <input id="id_form-__prefix__-nome" name="id_form-__prefix__-nome" type="text" />
    <input id="id_form-__prefix__-texto" name="id_form-__prefix__-texto" type="text" />
</div>

JavaScript

var elements = document.querySelectorAll('.form-modelo input');
for (var i = 0; i < elements.length; i++) {
    var el = elements[i];
    el.name = el.name.split('__prefix__').join(i);
    el.id = el.id.split('__prefix__').join(i);
    console.log(el.id, el.name);
}