Numbers not appearing when I click on their button

I’m trying to make a calculator and I have completed the html and css files so far however, whenever I click on a number button it is not displaying in the display. I am not sure where I went wrong, it most likely is a easy fix that I am just not seeing.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Cute Calculator</title>
    <link rel="stylesheet" href="style.css"/>
 </head>
 <body>
    <div id="calculator">
        <input id="display" readonly>
        <div id="keys">
            <button onclick="appendToDisplay('+')" class="op-button">+</button>
            <button onclick="appendToDisplay('7')">7</button>
            <button onclick="appendToDisplay('8')">8</button>
            <button onclick="appendToDisplay('9')">9</button>
            <button onclick="appendToDisplay('-')" class="op-button">-</button>
            <button onclick="appendToDisplay('4')">4</button>
            <button onclick="appendToDisplay('5')">5</button>
            <button onclick="appendToDisplay('6')">6</button>
            <button onclick="appendToDisplay('*')" class="op-button">*</button>
            <button onclick="appendToDisplay('1')">1</button>
            <button onclick="appendToDisplay('2')">2</button>
            <button onclick="appendToDisplay('3')">3</button>
            <button onclick="appendToDisplay('/')" class="op-button">/</button>
            <button onclick="appendToDisplay('0')">0</button>
            <button onclick="appendToDisplay('.')">.</button>
            <button onclick="calculate()">=</button>
            <button onclick="clearDisplay()" class="op-button">C</button>
        </div>
    </div>
    <script src="index.js"></script>
 </body>

</html>

body{
    margin:0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: url("./calckitty.jpg");
    background-size: cover;




}

#calculator{
    font-family: Arial, Helvetica, sans-serif;
    background: url("./kitty2.jpg");
    border-radius: 15px;
    max-width:500px;
    overflow:hidden;

}

#display{
    width:100%;
    padding:20px;
    font-size: 5rem;
    text-align: left;
    border:none;
    background: url("./kittytop.jpg");
    opacity: 90%;
    color:white;

}

#keys{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 5px;
    padding: 20px;
}

button{
    width:100px;
    height:100px;
    border-radius: 50px;
    border: 1.5px solid pink;
    background-color: hsl(26, 93%, 89%);
    color: rgb(128, 118, 118);
    font-size: 2rem;
    font-weight: bold;
    cursor: pointer;

}

button:hover{
    background-color: hsl(332, 60%, 77%);
}

button:active{
    background-color: hsl(332, 60%, 83%);
}

.op-button{
    background-color: hsl(327, 44%, 35%);
}

.op-button:hover{
    background-color: hsl(327, 59%, 45%);
}

.op-button:active{
    background-color: hsl(57, 54%, 58%);
}
const display = document.getElementById("display");

function appendToDisplay(input){
 display.value += input;
 console.log;
 
}

function clearDisplay(){

}

function calculate(){

}

I went through my html file, made sure the .js and .html file were linked, they were and then I went back to make sure my ids were correct and they are.