D3 Examples - d3-brush example

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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
</head>
<body>
​
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.3/d3.min.js"></script>
​
<script>
  
// set drawing region dimensions  
var width = 400, height = 400;
​
// create drawing region svg
var svg = d3.select("body")
            .append("svg")
            .attr("width", width)
            .attr("height",height);
​
// add outer black box
svg.append("rect")
   .attr("width",width)
   .attr("height",height)
   .style("fill","none")
   .style("stroke","black");
​
// create brush 
var brush = d3.brush();
  
// set brush extend (0,0) is top left corner
brush.extent([[0, 0], [ width, height]]);
  
// attach events  
brush  
    .on("start brush", brushing)
    .on("end", brushend);
​
// call brush on selection  
svg.append("g")
    .call(brush);
​
// during brushing send coordinates to console
function brushing() {
  // console.log( d3.event.selection );
  var s = d3.event.selection,
      x0 = s[0][0],
      y0 = s[0][1],
      x1 = s[1][0],
      y1 = s[1][1],
      dx = s[1][0] - x0,
      dy = s[1][1] - y0;
  console.log("("+x0+","+y0+")-("+x1+","+y1+")");
}
​
// on brush end, console log if no selection
function brushend() {
  console.log('end');
  if (!d3.event.selection) {
    console.log('There is no selection');
  }   
}  
</script>    
  
</body>
</html>
    