Appendix JS_F_A5

Requirement: If an input error is detected, the field should be identified and the error described in text.

Details: Do not force the focus to remain in invalid fields.

<form action="#">
    <fieldset>
        <p>
            <label for="demo">Number field:</label>
            <input id="demo" name="demo" type="text" />
        </p>
    </fieldset>
</form>

var input = document.getElementById('demo');
 
input.addEventListener('blur', function(e)
{
    if(input.value && !/^[\d]+$/.test(input.value))
    {
        window.setTimeout(function()
        {
            input.focus();
 
        }, 10);
    }
}, false);