How to apply a background color to an <input> when it is filled

Hey everyone!

I really hope someone can stop me from pulling my hair off. I am trying to apply a background-color to an input field when it has something in it:

Say I have an input field for username like this:

<form>
  <label for="login-username">Username</label>
  <input type="text" id="login-username">
</form>

So say I have a default background of #fff, and whenever a user types anything on the input field it will turn yellow even though they will click on the next input field.

Some sort of a visual feedback that "this field is filled".

I already tried researching this topic but to no avail. I am asking you guys to help me out because I know for sure that this can be achieve with jQuery.

I'm sorry but my jQuery knowledge is still very primitive so I am asking help from you guys.

Thanks for dropping your answers! really appreciate any help!