performance optimization of snap points using drag and drop in RaphealJS

I have a demo page where I am looking at the performance of around 300 points that an object should snap to when being dragged.

http://jsfiddle.net/digiguru/rVFje/

I have optimized it by loading the bounds of each "snap" point into 4 arrays when the drag is started.

var circleT = [];
var circleR = [];
var circleB = [];
var circleL = [];

var start = function (event) {
    this.ox = this.attr("cx");
    this.oy = this.attr("cy");
    var threshold = 15;

    for (var myCircle in circles) {
        circleT[myCircle] = circles[myCircle].attr("cy") - threshold;
        circleR[myCircle] = circles[myCircle].attr("cx") + threshold;
        circleB[myCircle] = circles[myCircle].attr("cy") + threshold;
        cir开发者_JAVA技巧cleL[myCircle] = circles[myCircle].attr("cx") - threshold;
    }
    circle.animate({ r: 20,fill: "#319F40", "stroke-width": 1 }, 200);
},

Then in the move event we use the following to calculate the dragged object from each of the snap points...

move = function (mx, my) {
    var inrange = false; 
    var mouseCX = this.ox + mx;
    var mouseCY = this.oy + my;
    var lockX = 0;
    var lockY = 0;

   for (var myCircle in circles) {
        if ((circleT[myCircle] < mouseCY
             && circleB[myCircle] > mouseCY ) 
            && (circleR[myCircle] > mouseCX 
                && circleL[myCircle] < mouseCX )) {
           inrange = true; 
           lockX =  circles[myCircle].attr("cx");
           lockY =  circles[myCircle].attr("cy");
        }
    }
    if (inrange) {
         this.attr({
            cx: lockX ,
            cy: lockY 
        });
    } else {
        this.attr({
            cx: mouseCX ,
            cy: mouseCY 
        });
    }

}, 

Genrally performance, is good, but you can notice frames dropping on slightly older IE browsers (IE8 and below). Is there a ninja way to improve performance at all? Perhaps I can improve the 4 if statements? Would using another javascript library like processing JS yeild better results?

---

Currently you consider every circle on every iteration. You could improve performance by considering fewer circles using a technique similar to this.

http://en.wikipedia.org/wiki/Quadtree

Basically, create bounding boxes for collections of circles. If the circle you are dragging is out of bounds then don't consider any circle within the bounding box. I hope this helps.