jQuery Validate plugin, enable submit button when form is valid

You would simply construct a blur (or even a keyup) handler function to toggle the button based on the form's validity. Use the plugin's .valid() method to test the form.

$('input').on('blur', function() {
    if ($("#myform").valid()) {
        $('#submit').prop('disabled', false);  
    } else {
        $('#submit').prop('disabled', 'disabled');
    }
});

DEMO: http://jsfiddle.net/sd88wucL/

---

Instead, you could also use both events to trigger the same handler function...

$('input').on('blur keyup', function() {
    if ($("#myform").valid()) {
        $('#submit').prop('disabled', false);  
    } else {
        $('#submit').prop('disabled', 'disabled');
    }
});

DEMO 2: http://jsfiddle.net/sd88wucL/1/

Source: https://stackoverflow.com/a/21956309/594235