Defining custom easing in code

Part of my project includes a slider that is dynamically given a position. Because this all happens in code, I can't use the timeline tool to change the easing to something like "easeOutBounce."

This seems to follow the jQuery convention but results in the standard easing:

sidebarSymbol.$("slider").animate({top: sidebarSymbol.sliderPositions[scene]}, 750, "easeOutBounce", sym.playNext());

What am I missing?