Popup window with HTML+CSS+JS (pug, stylus, jquery)

popup.js

$('button[data-popup]').click(function(){
    $('.popup[data-popup="' + $(this).data('popup') + '"]').fadeIn('fast');
});

$('.popup .close').click(function() {
    $(this).parent().parent().fadeOut('fast');
});

$( '.popup' ).mousedown(function(e) {
    if (!$(e.target).closest('.window').length ) {
        $(this).fadeOut('fast');
    }
});

popup.pug

button(data-popup="form-order")

<!-- ... -->

.popup(data-popup="form-order")
    .window
        .close
        // form content

popup.styl

.popup
    display: none
    width: 100%
    height: 100%
    position: fixed
    left: 0
    top: 0
    overflow: auto
    z-index: 1000
    text-align: center
    background-color: rgba(0,0,0,0.8)

    .window
        background-color: #FFFFFF
        vertical-align: middle
        padding: 1em
        max-width: 750px
        width: 100%
        position: relative
        margin: 50px auto 0

        .close
            height 24px
            width 51px
            position absolute
            cursor: pointer
            right 0px
            top 0px
            z-index 1001
            background url( %%FILEPATH%% ) no-repeat top center;
            &:hover
                background-position: bottom center;