Detecting Browser Autofill

Question

How do you tell if a browser has auto filled a text-box? Especially with username & password boxes that autofill around page load.

My first question is when does

Answer 1

I also faced the same problem where label did not detect autofill and animation for moving label on filling text was overlapping and this solution worked for me.

input:-webkit-autofill ~ label {
    top:-20px;
}