这句话我该如何理解

objX = parseInt($('source_div').style.left || $('source_div').offsetLeft) || 0,$addEvent(document,'click',function(event){
                var evt = window.event || event
                   traceX = evt.clientX,
                   traceY = evt.clientY,                                                                                                    
                   objX = parseInt($('source_div').style.left || $('source_div').offsetLeft) || 0,
                   objY = parseInt($('source_div').style.top ||  $('source_div').offsetTop) || 0,
                   distance = Math.sqrt(Math.pow(traceX-objX ,2)+Math.pow(traceY-objY,2)),
                   //sin
                   s = (traceY-objY)/distance, 
                   //cos
                   c = (traceX-objX)/distance,
                   t = 0;
                clearInterval(st);