index.html

<!DOCTYPE html>
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<html>
    <head>
        <title>TODO supply a title</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
    </head>
    <body>
        <div id="js">TODO write content</div>
        <script>
            var x = 5;
            var y = "2";
            var z = x+y;
            console.log(z);

             document.getElementById("js").innerHTML= z;

             function provera(){
                 var user= "admin";
                 var pass= "pass";

                 var inputUser = document.getElementById("user").value;
                 var inputPass = document.getElementById("pass").value;

                 if(user== inputUser && pass==inputPass){
                       alert("Uspesan Login");
                       console.log("Uspesan login");
                 }else{
                     console.log("Greska sa loginom");
                 }
             }
        </script>

        <label>Korisnicko ime</label>
        <input type="text" id="user">
        <br>
         <label>Lozinka</label>
         <input type="password" id="pass">
         <br>
         <button type="button" onclick="provera()">Uloguj se</button>

    </body>
</html>