I have a plugin in some pages but in some other pages I don't want it so I didn't reference its script file.

How to check if the plugin functions exist before using it.

In my case I am using this plugin: and I use it like this:

$('#marquee-inner div').marquee('pointer').mouseover(function() {

    $(this).trigger('stop');

}).mouseout(function() {

    $(this).trigger('start');

}).mousemove(function(event) {

    if ($(this).data('drag') == true) {

        this.scrollLeft = $(this).data('scrollX') + ($(this).data('x') - event.clientX);

    }

}).mousedown(function(event) {

    $(this).data('drag', true).data('x', event.clientX).data('scrollX', this.scrollLeft);

}).mouseup(function() {

    $(this).data('drag', false);

});

What I want is to make a check before calling this marquee function if it exist or not.