Simplest validation for Safari and <=IE9

simplevalidation.js

//// Validation 
if (typeof document.createElement('input').checkValidity === 'function') {
    $('form').submit(function (e) {
        if (!this.checkValidity()) {
            e.preventDefault();
            alert('Some fields are invalid. Please check your form again. ');
        }
    });
} else {
    $('form').submit(function (e) {
        errors = $(this)
           .find("input:not([type=radio]):not([type=checkbox]), select, textarea")
           .filter("[required]")
           .filter(function() { return ($(this).val() ? false : true); });
        if (errors.length > 0) {
            e.preventDefault();
            alert('Some fields are invalid. Please check your form again.');
        }
    });
}