UpdateValueInTexField.html

  
 <!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="utf-8">
    <title>Update Value in Text Field</title>
</head>

<body onload="main()">
    <form>
        Enter Value
        <input type="text" id="myTextField" value="4"><br><br>
        <input type="button" id="ComputeValueButton" value="Compute Sqrt"> 
        (press button multiple times and look at textfield)<br><br>
        <input type="reset" value="Reset">
    </form>
    <script>

        function main() {
            document.getElementById("ComputeValueButton").onclick = displayValue; // DO NOT PUT ()
        }

        function displayValue() {
            let myTextFieldElement = document.getElementById("myTextField");
            let textProvided = myTextFieldElement.value;
            let numericValue = Number(textProvided);

            /* Updating the textfield */
            myTextFieldElement.value = Math.sqrt(numericValue);
        }
    </script>
</body>

</html>