If an array of coordinates is clockwise, convert it to counterclockwise.

counterclockify.js

/*

Make coordinates counter-clockwise

http://stackoverflow.com/questions/1165647/how-to-determine-if-a-list-of-polygon-points-are-in-clockwise-order

(x2-x1)(y2+y1)

point[0] = (5,0)   edge[0]: (6-5)(4+0) =   4
point[1] = (6,4)   edge[1]: (4-6)(5+4) = -18
point[2] = (4,5)   edge[2]: (1-4)(5+5) = -30
point[3] = (1,5)   edge[3]: (1-1)(0+5) =   0
point[4] = (1,0)   edge[4]: (5-1)(0+0) =   0
                                         ---
                                         -44  counter-clockwise

 */

// counter
var arr1 = [{x:-117.99520254135132,y:34.000304304410228},{x:-117.99455881118774,y:33.997280094622781},{x:-117.98940896987915,y:33.99770704841373},{x:-117.99000978469849,y:34.001940890690349},{x:-117.99520254135132,y:34.000304304410228}];

// clock
var arr2 = [{x:-118.02886962890625,y:33.884097379274905},{x:-117.78717041015625,y:33.93424531117312},{x:-117.91351318359375,y:33.80653802509606},{x:-117.75970458984375,y:33.77914733128647},{x:-118.00689697265625,y:33.687781758439364}];

var isClock = function (arr) {
	var sums = [];
	var sum = 0;
	var len = arr.length;
	var i2 = function (cur) {
		if ((cur+1) >= len) return 0;
		return (cur+1);
	};
	for (var i=0; i < len; i++) {
		// (x2-x1)(y2+y1)
		sums.push( (arr[i2(i)].x - arr[i].x) * (arr[i2(i)].y + arr[i].y)  );
	}
	for (k in sums) sum += sums[k];
	console.log(sum);
	return (sum > 0); 
};

var makeCounterClock = function (arr) {
	if (isClock(arr)) {
		console.log('clockwise, fixed');
		var cc = [];
		for (var i=(arr.length-1); i > -1; i-- ) {
			cc.push(arr[i]);
		}
		return cc;
	} else {
		console.log('counter-clockwise already');
		return arr;
	}
};

console.log( arr1 );
console.log( makeCounterClock(arr1) );
console.log( arr2 );
console.log( makeCounterClock(arr2) );