value in input is undefined-CodePudding

I'm making AP calculator but the answer value is undefined in the input field of answer having id "An" please help; here's my code:

<!doctype html>
<html>

<head>
    <meta charset="utf-8">
    <title>JavaScript Example</title>
</head>

<body>
    <!-- first term -->
    <input type="text" value="1" name="" id="a1" onkeyup="ap()">
    <!-- number of term -->
    <input type="text" value="2" name="" id="n" onkeyup="ap()">
    <!-- difference -->
    <input type="text" name="" value="3" id="d" onkeyup="ap()">
    <input type="text" name="" id="An">

    <script>
        ap()

        function ap() {
            let a1 = document.getElementById("a1").value;

            let n = document.getElementById("n").value;
            let d = document.getElementById("d").value;
            var An = Number(a1)   ((Number(n) - 1) * Number(d));
            console.log(An)
            document.getElementById("An").value = An.value
        }
    </script>
</body>

</html>

please help in solving the issue.

CodePudding user response：

Change the An.value to jut An, since An is just a variable

document.getElementById("An").value = An;

CodePudding user response：

You must assign the variable 'An' direct in the value.

document.getElementById("An").value = An