jQuery check if element is on screen

is-on-screen.js

/**
  * @desc checks if current element is on screen or within viewport
  * @param none
  * @return int - the coordinates of the window vs. the element
*/
jQuery.fn.isOnScreen = function(){
	     
    var win = $(window);
	     
    var viewport = {
        top : win.scrollTop(),
        left : win.scrollLeft()
    };
    viewport.right = viewport.left + win.width();
    viewport.bottom = viewport.top + win.height();
	    
    var elemtHeight = this.height()/2;// Get half of the height of current element
    elemtHeight = Math.round(elemtHeight);// Round it to whole humber
	     
    var bounds = this.offset();// Coordinates of current element
    bounds.top = bounds.top + elemtHeight;// Top is redefined as half of current element's height
    bounds.right = bounds.left + this.outerWidth();
    bounds.bottom = bounds.top + this.outerHeight();
	    	     
    return (!(viewport.right < bounds.left || viewport.left > bounds.right || viewport.bottom < bounds.top || viewport.top > bounds.bottom));
     
}

// Usage:
$(window).scroll(function(){
    if( $('#my-div').isOnScreen() ){
 	  // do something
    }
});