dump.js

const rgx = /virtual\s+(\w+)\s*\*?\s+\*?(\w+)\(([^)]+)\)/g;
const foo = document.getElementById("area");
const textarea = document.getElementById("code");
const btn = document.getElementById("btn");
btn.onclick = function() {
	const code = textarea.value;
	let submissions = code.matchAll(rgx);
  
  const outputs = [];
  let ind = 0;
  for(const [full, ret, name, params] of submissions) {
  	outputs.push(`#[virtual_index(${ind})] pub fn ${name}(${params}) -> ${ret} {}`);
    ind++;
  }

	foo.value = outputs.join("\n");
};