Internal topoJSON borders used .mesh vs .merge

## elasticSVG.js
(function() {
    var root = this;

	// create a new SVG element
	var elasticSVG = function(selector, opts) {
		opts = opts || {};

		// containing DOM element, which defaults to body
		var parent = document.querySelectorAll(selector || "body");

		if (!parent || !parent.length) {
			console.log("Couldn't find a parent for elasticSVG making the selector '" + selector + "'");
			return;
		}

		parent = parent[0];

		// you can specify a width if you like, or we'll snap to size of container
		var base = {
			width: typeof opts.width !== "undefined" ? opts.width : parent.clientWidth,
			scale: 1
		};

		// we need to remember the original width for scaling purposes
		base.original_width = base.width;

		// you can either specify the height or the aspect ratio. If neither is specified, refaults to roughly the golden ratio
	    if (typeof opts.height !== "undefined") {
	    	base.height = opts.height;
	    	opts.aspect = base.height / base.width;
	    } else {
		    opts.aspect = typeof opts.aspect !== "undefined" ? opts.aspect : 0.618;
			base.height = base.width * opts.aspect;
	    }

        var xmlns = "http://www.w3.org/2000/svg";
        var svg = document.createElementNS(xmlns, "svg");
		svg.setAttributeNS(null, "width", base.width);
		svg.setAttributeNS(null, "height", base.height);
		parent.appendChild(svg);

		// setting resize to "auto" sets the viewport to the original width and height so that the SVG always scales
	    if (opts.resize && opts.resize == "auto") {
			svg.setAttributeNS(null, "viewBox", "0 0 " + base.width + " " + base.height);
	    }

		function resize() {
			console.log(parent)
			base.width = parent.clientWidth;
		    base.height = base.width * opts.aspect;
		    base.scale = base.width / base.original_width;

			svg.setAttributeNS(null, "width", base.width);
			svg.setAttributeNS(null, "height", base.height);

			// optional callback
			if (opts.onResize) {
				opts.onResize(base.width, base.height, base.scale);
			}
		}

		var resizeTimer;

		// http://stackoverflow.com/questions/3339825/what-is-the-best-practise-to-not-to-override-other-bound-functions-to-window-onr
		function addResizeEvent(func, dur) {
		    var oldResize = window.onresize,
				resizeTimer,
				dur = typeof dur === "undefined" ? 250 : parseInt(dur, 10);

			window.onresize = function () {
				clearTimeout(resizeTimer);

		        if (typeof oldResize === 'function') {
		            oldResize();
		        }

				resizeTimer = setTimeout(function() {
					func();
				}, dur);
			}
		}

		addResizeEvent(resize, 250);

		if (opts.resize && opts.resize === "auto") {
			resize(); // call this on load since sometimes the initial conditions are wider than container
		}

		base.setResize = function(f) {
			opts.onResize = f;
		}

		base.svg = svg;
		return base;
	}

	// support various modular environments
	if (typeof define === "function" && define.amd) { // RequireJS
	    define(elasticSVG);
	} else if (typeof module === "object" && module.exports) { // browserify
	    module.exports = elasticSVG;
	} else {
	    root.elasticSVG = elasticSVG; // directly included
	}

}());

## index.html
<!DOCTYPE html>
	<head>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0">
		<title>TopoJSON Counties With Organic Borders</title>
		<style>

path.county {
  fill: #eee;
  stroke: #fff;
  stroke-width: .5px;
}

path.state {
	fill: none;
	stroke: #404040;
	stroke-width: 1px;
}

.Example {
	max-width: 900px;
	width: 100%;
	height: 1500px;
}

.title {
	font-size: 24px;
	font-family: Arial;
	text-align: center;
}


		</style>

	</head>
	<body>
		<div class="Example">
			<div class="title">Merged</div>
			<div id="map_merged"></div>
			<div class="title">Meshed</div>
			<div id="map_meshed"></div>
		</div>
		<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
		<script src="https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js"></script>
		<script src="elasticSVG.js"></script>
		<script>
			var projection = d3.geo.albersUsa()
			    .scale(1200)
			    .translate([450, 275]);

			var path = d3.geo.path().projection(projection);
			d3.json("us.json", function(error, topology) {
				if (error) throw error;

				// MESHED

				// make the SVG responsive
				var el_meshed = elasticSVG("#map_meshed", {
					width: 900,
					aspect: 0.65,
					resize: "auto"
				});

				var svg_meshed = d3.select(el_meshed.svg).append("g");

				//meshed
				var counties = topojson.feature(topology, topology.objects.counties).features;


				svg_meshed.selectAll("path")
			    	.data(counties)
			    	.enter().append("path")
			    	.attr("class", "county")
			    	.attr("d", path)
			    	.on("click", function(d) {
			    		console.log(d);
			    	});

				svg_meshed.append("path")
					.datum(topojson.mesh(topology, topology.objects.counties, function(a, b) { return a.id - a.id % 1000 !== b.id - b.id % 1000; }))
					.attr("class", "state")
					.attr("d", path);


				// MERGED

				// make the SVG responsive
				var el_meshed = elasticSVG("#map_merged", {
					width: 900,
					aspect: 0.65,
					resize: "auto"
				});

				var svg_merged = d3.select(el_meshed.svg).append("g");

				//meshed
				svg_merged.selectAll("path")
			    	.data(counties)
			    	.enter().append("path")
			    	.attr("class", "county")
			    	.attr("d", path);

			    // let's get an organic list of fips
			    var fips = {};
			    counties.forEach(function(county) { fips[county.id - county.id % 1000] = 1; });

			    var states = [];
			    // and merge by fips
				Object.keys(fips).forEach(function(fip) {
					var state = topojson.merge(topology, topology.objects.counties.geometries.filter(function(d) { return d.id - d.id % 1000 == fip; }));
					states.push(state);
				});

				svg_merged.append("g").attr("id", "states").selectAll(".state").append("path")
					.data(states)
					.enter()
					.append("path")
					.attr("class", "state")
					.attr("d", function(d) {
						return path(d);
					});
			});
		</script>
	</body>
</html>

## us.json

      
          Raw
        
        
              us.json
            
          
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