[jQuery] why this can't stop user leave from input field

[jQuery] why this can't stop user leave from input field


Hi, all
Why can't the following stop users from leaving input field1? How can
I stop users from leaving a input field if I find something wrong?
Thak you inadvance!
$(document).ready(function(){
        $('input[name=field1]').blur(function(event){
                console.log('leaving');
                event.preventDefault();
            });
});
jack