How do I replace the "NaN" value with "error" or something like it? (For ecample when ypu press valculate without parameter)

Question

https://code.sololearn.com/WTFyM95eGJw6/?ref=app

Answer 1

if (isNaN(calculate)) {calculate = "Err"}
document.querySelector("#result").innerHTML = calculate;

Answer 2

You should first change the input type from text to number:
type="number"

And then just add an error handling in your code, you can check with JS, if either the input or your result is a number and print something different if not.