Untitled

<!DOCTYPE html>
<html>
    <head>
        <title>Kalkulator - JS</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
    </head>
    <body>
        <input type="text" id="ekran" readonly="readonly"/>
        <input type="text" id="prviBroj" hidden="hidden"/>
        <input type="text" id="operand" hidden="hidden"/>
        <br />

        <input type="button" value="7" onclick="dodajBroj(7)"/>
        <input type="button" value="8" onclick="dodajBroj(8)"/>
        <input type="button" value="9" onclick="dodajBroj(9)"/>
        <input type="button" value="+" onclick="operacija('+')"/>
        <br />
        <input type="button" value="4" onclick="dodajBroj(4)"/>
        <input type="button" value="5" onclick="dodajBroj(5)"/>
        <input type="button" value="6" onclick="dodajBroj(6)"/>
        <input type="button" value="-" onclick="operacija('-')"/>
        <br />
        <input type="button" value="1" onclick="dodajBroj(1)"/>
        <input type="button" value="2" onclick="dodajBroj(2)"/>
        <input type="button" value="3" onclick="dodajBroj(3)"/>
        <input type="button" value="*" onclick="operacija('*')"/>
        <br />
        <input type="button" value="0" onclick="dodajBroj(0)"/>
        <input type="button" value="C"/>
        <input type="button" value="="/>
        <input type="button" value="/" onclick="operacija('/')"/>

        <script>
            function dodajBroj(broj){
                document.getElementById("ekran").value += broj;
            }
            function operacija(operand){
                document.getElementById('prviBroj').value= document.getElementById('ekran').value;

                document.getElementById('operand').value=operand;
                document.getElementById('ekran').value="";
            }
            function izracunaj
        </script>

    </body>
</html>