jQuery expressions or Responsive Web Design is a jQuery plugin intended to aid responsive web design practices. Specifically, the plugin enables the user to identify page elements that are inside or outside the user's current viewport.
Some example use cases are:
-Lazy loading content based on a user's scrolling activity
This might included loading products as a user scrolls on a category listings or search results page.
-Performing DOM manipulations on elements currently in the user's viewport
This may include adding JS-based animations or event based functions.
Please see the example page for more info.