CODE EXAMPLE FOR JAVASCRIPT

javascript only allow numbers

function onlyNumbers(e) {
    // Check if the user pressed a number
    if (e.which != 8 && e.which != 0 && (e.which < 48 || e.which > 57)) {
        // If the user pressed a number, prevent the default action
        e.preventDefault();
    }

    // Then, add the event listener to the input
    document.getElementById("input").addEventListener("keypress", onlyNumbers);

        // If the key pressed is not a number, prevent the default action
        if (e.which != 8 && e.which != 0 && (e.which < 48 || e.which > 57)) {
            e.preventDefault();
        }

        // If the key pressed is a number, allow the default action
        if (e.which == 8 || e.which == 0 || (e.which >= 48 && e.which <= 57)) {
            return;
        }
    }

// Call the function
onlyNumbers(e);