[jQuery] check if checkbox is checked dynamicallyH

[runrunforest]

Hi,

I have a html like this

<input type="checkbox" id="priority" /><span class="presult">0 USD</
span>

I want when checkbox is checked, the span will have 500 USD. When
checkbox is unchecked the span will return 0 USD.

This is what I've got, have no idea why not work.

if ($('#priority').is(':checked')) {
            $('.presult').text('500 USD');
    }else {
        $('.presult').text('');
    }