JSFiddle - React, Tailwind, and code Playground

HTML

<html>
 <body>
 <input type="number" id="val1" >
 <input type="number" id="val2" >
 <input type="text"   id="prefx" >
 <input type="button" value="Lancer" onclick="run();">
 <div id="list"></div>
 <a id="lienFichier" download="fichier.csv" href="#">CSV</a>
 </body>
</html>

CSS

a#lienFichier {
  display: none;
}

JavaScript

var csvHref = "data:application/octet-stream,Compteur;Genereration%0A";
 
 function run(){
   var l1,i=0,v1,v2,newline,n0,prefx;
   v1=Number(document.getElementById("val1").value);
   v2=Number(document.getElementById("val2").value);
   prefx=document.getElementById("prefx").value;
   l1=v1.toString().length;
   var divlist = document.getElementById("list");
   if(l1 < v2){
     while(i.toString().length <= (v2-l1)){
     n0=nb0(v2-l1-i.toString().length)
     //newline = divlist.appendChild(document.createElement("div"));
     //newline.innerHTML = prefx + v1 + "" + n0 + "" + i;
     csvHref += i + ";" + prefx + v1 + "" + n0 + "" + i + "%0A";
     i++;
     }
     document.getElementById("lienFichier").href = csvHref;
     document.getElementById("lienFichier").style.display = 'block';
   }
 }
 function nb0(nb){
   var val="";
   for(var i=0;i<nb;i++)
   	val+="0";
   return val;
 }