JSFiddle - React, Tailwind, and code Playground

HTML

<body onload="VerificaCookie();">
    <button onclick="PrintCookies();">Tutti i cookie</button>
    <br />
    <br />
    <input id="myinput" type="text" name="myinput" size="20" maxlength="30" value="Messaggio..." />
    <button onclick="send();">Send</button>
    <br />
    <br /><span id="msg"></span>
</body>

JavaScript

function send() {
     var valore = document.getElementById("myinput").value;
     var adesso = new Date();
     adesso.setTime(adesso.getTime() + (1000 * 60 * 60 * 24 * 30));
     document.cookie = "valore=" + encodeURIComponent(valore) + "; expires=" + adesso.toGMTString();
     document.getElementById("msg").innerHTML = valore;
 }

 function GetCookies() {
     var name_valuePairs = [];

     var cookiesArr = document.cookie.split("; ");
     for (var i = 0; i < cookiesArr.length; i++) {
         var name_valueStr = cookiesArr[i];
         var name_valeArr = name_valueStr.split("=");
         name_valuePairs[name_valeArr[0]] = decodeURIComponent(name_valeArr[1]);
     }

     return (name_valuePairs);
 }

 function PrintCookies() {
     alert(document.cookie);
 }

 function VerificaCookie() {
     if (!window.navigator.cookieEnabled) {
         alert("Non hai i cookie abilitati.");
     } else {
         var cookies = GetCookies();
         if (undefined !== cookies["valore"]) {
             document.getElementById("msg").innerHTML = cookies["valore"];
         }
     }
 }