svgPathLength.js

Object.defineProperty(SVGPolygonElement.prototype, 'pathLength', {
	get: function(){
		var numPoints = this.points.length || this.points.numberOfItems;
		var l = 0;
		for (var i = 1; i < numPoints; i++) {
			var point2 = this.points[i] || this.points.getItem(i);
			var point1 = this.points[i-1] || this.points.getItem(i-1);
			l += Math.sqrt(Math.pow(Math.abs(point2.x-point1.x),2)+Math.pow(Math.abs(point2.y-point1.y),2));
		}
		return l;
	},
	set: function(val){ return undefined; }
});

Object.defineProperty(SVGCircleElement.prototype, 'pathLength', {
	get: function(){
		return 2*Math.PI*this.getAttribute("r");
	},
	set: function(val){ return undefined; }
});

Object.defineProperty(SVGRectElement.prototype, 'pathLength', {
	get: function(){
		return 2*this.getAttribute("width")+2*this.getAttribute("height");
	},
	set: function(val){ return undefined; }
});