JSFiddle - React, Tailwind, and code Playground

HTML

<button id="attack_enabled">ATTACK</button>
<button id="restore_enabled">RESTORE</button>

<div class="territory_middle_complete">ADD A CLASS HERE</div>

JavaScript

$("#attack_enabled").click(function(){
   createCookie('attackcompletecookie','attack_cookie');
});

$("#restore_enabled").click(function(){
   createCookie('restorecompletecookie','restore_cookie');
   var atkcomplete = readCookie('attackcompletecookie');
   if(atkcomplete)
   {
       alert(atkcomplete);
       $(".territory_middle_complete").addClass("displayblockzindex2");
    }
});

function createCookie(cookieName, cookieId) {
    document.cookie = cookieName + '=' + cookieId;
}

function readCookie(name) {
    var nameEQ = encodeURIComponent(name) + "=";
    var ca = document.cookie.split(';');
    for (var i = 0; i < ca.length; i++) {
        var c = ca[i];
        while (c.charAt(0) === ' ') c = c.substring(1, c.length);
        if (c.indexOf(nameEQ) === 0) return decodeURIComponent(c.substring(nameEQ.length, c.length));
    }
    return null;
}