MB zoom circles in and out

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forked from Igathi's block: MB zoom circles in and out

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.background {
  fill: none;
  pointer-events: all; 
}

.feature {
  fill: #ccc;
  cursor: pointer;
}

</style>
<body>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://d3js.org/topojson.v1.min.js"></script>
<script>

var svg = d3.select("body").append("svg")
     
 svg.attr("width", width)
    .attr("height", height)
    .on("click", stopped, true);
 
 svg.append("rect")
    .attr("class", "background")
    .attr("width", width)
    .attr("height", height)
		.style("fill", "white")
		.style("stroke", "black")
    .on("click", reset);
  
var g = svg.append("g");

svg
    .call(zoom) // delete this line to disable free zooming
    .call(zoom.transform, initialTransform);

svg.transition()
     .duration(750)
     .call(zoom.transform, transform);
}

function reset() {
  active.classed("active", false);
  active = d3.select(null);

svg.transition()
      .duration(750)
      .call(zoom.transform, initialTransform);
}

function zoomed() {
  var transform = d3.event.transform;

g.style("stroke-width", 1.5 / transform.k + "px");
  g.attr("transform", transform);
}

// If the drag behavior prevents the default click,
// also stop propagation so we don’t click-to-zoom.
function stopped() {
  if (d3.event.defaultPrevented) d3.event.stopPropagation();
}

</script>

https://d3js.org/d3.v4.min.js

https://d3js.org/topojson.v1.min.js