Brush and zoom in d3 v4

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    .area {
      fill: none;
      clip-path: url(#clip);
      stroke: #444;
      stroke-width: 2px;
    }
    
    .zoom {
      cursor: move;
      fill: none;
      pointer-events: all;
    }
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <svg width="960" height="500"></svg>
  <script>
    var dataJSON = {
    "columns": [
        "date",
        "value"
    ],
    "values": [
        [
            "1986-06-02",
            "0.40200000000000000000"
        ],
        [
            "1986-06-03",
            "0.39300000000000000000"
        ],
        [
            "1986-06-04",
            "0.37800000000000000000"
        ],
        [
            "1986-06-05",
            "0.39000000000000000000"
        ],
        [
            "1986-06-06",
            "0.38500000000000000000"
        ],
        [
            "1986-06-09",
            "0.37300000000000000000"
        ],
        [
            "1986-06-10",
            "0.36500000000000000000"
        ],
        [
            "1986-06-11",
            "0.38900000000000000000"
        ],
        [
            "1986-06-12",
            "0.39400000000000000000"
        ],
        [
            "1986-06-13",
            "0.39800000000000000000"
        ],
        [
            "1986-06-16",
            "0.37900000000000000000"
        ],
        [
            "1986-06-17",
            "0.37400000000000000000"
        ],
        [
            "1986-06-18",
            "0.37600000000000000000"
        ],
        [
            "1986-06-19",
            "0.38200000000000000000"
        ],
        [
            "1986-06-20",
            "0.36500000000000000000"
        ],
        [
            "1986-06-23",
            "0.36900000000000000000"
        ],
        [
            "1986-06-24",
            "0.36900000000000000000"
        ],
        [
            "1986-06-25",
            "0.37500000000000000000"
        ],
        [
            "1986-06-26",
            "0.37600000000000000000"
        ],
        [
            "1986-06-27",
            "0.37900000000000000000"
        ],
        [
            "1986-06-30",
            "0.37400000000000000000"
        ],
        [
            "1986-07-01",
            "0.36900000000000000000"
        ],
        [
            "1986-07-02",
            "0.35900000000000000000"
        ],
        [
            "1986-07-03",
            "0.34900000000000000000"
        ]
    ]
}; 
    var testData = [];
    var parseDate = d3.timeParse("%Y-%m-%d");
    var parseDate2 = d3.timeParse("%b %Y");
    var formatDate = d3.timeFormat('%b %Y');
    
    dataJSON.values.forEach(function(d){
    
      var item = {}; 
      item['date'] = parseDate2(formatDate(parseDate(d[0])));
      item['price'] = d[1];
      testData.push(item); 
        
    }); 
    
    console.log(testData);
    
    var svg = d3.select("svg");
    var margin = {top: 20, right: 20, bottom: 110, left: 40};
    var margin2 = {top: 430, right: 20, bottom: 30, left: 40};
    var width = +svg.attr("width") - margin.left - margin.right;
    var height = +svg.attr("height") - margin.top - margin.bottom;
    var height2 = +svg.attr("height") - margin2.top - margin2.bottom;
    
    var x = d3.scaleTime().range([0, width]),
    x2 = d3.scaleTime().range([0, width]),
    y = d3.scaleLinear().range([height, 0]),
    y2 = d3.scaleLinear().range([height2, 0]);
    
    var xAxis = d3.axisBottom(x),
    xAxis2 = d3.axisBottom(x2),
    yAxis = d3.axisLeft(y);

var brush = d3.brushX()
    .extent([[0, 0], [width, height2]])
    .on("brush end", brushed);

var zoom = d3.zoom()
    .scaleExtent([1, Infinity])
    .translateExtent([[0, 0], [width, height]])
    .extent([[0, 0], [width, height]])
    .on("zoom", zoomed);

var area = d3.line()
    //.curve(d3.curveMonotoneX)
    .x(function(d) { return x(d.date); })
    //.y0(height)
    .y(function(d) { return y(d.price); });

var area2 = d3.area()
    .curve(d3.curveMonotoneX)
    .x(function(d) { return x2(d.date); })
    .y0(height2)
    .y1(function(d) { return y2(d.price); });

svg.append("defs").append("clipPath")
    .attr("id", "clip")
  .append("rect")
    .attr("width", width)
    .attr("height", height);
var focus = svg.append("g")
    .attr("class", "focus")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var context = svg.append("g")
    .attr("class", "context")
    .attr("transform", "translate(" + margin2.left + "," + margin2.top + ")");
    
    
  x.domain(d3.extent(testData, function(d) { return d.date; }));
  y.domain([0, d3.max(testData, function(d) { return d.price; })]);
  x2.domain(x.domain());
  y2.domain(y.domain());

focus.append("path")
      .datum(testData)
      .attr("class", "area")
      .attr("d", area);

focus.append("g")
      .attr("class", "axis axis--x")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

focus.append("g")
      .attr("class", "axis axis--y")
      .call(yAxis);

context.append("path")
      .datum(testData)
      .attr("class", "area")
      .attr("d", area2);

context.append("g")
      .attr("class", "axis axis--x")
      .attr("transform", "translate(0," + height2 + ")")
      .call(xAxis2);

context.append("g")
      .attr("class", "brush")
      .call(brush)
      .call(brush.move, x.range());

svg.append("rect")
      .attr("class", "zoom")
      .attr("width", width)
      .attr("height", height)
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")")
      .call(zoom);

function brushed() {
  if (d3.event.sourceEvent && d3.event.sourceEvent.type === "zoom") return; // ignore brush-by-zoom
  var s = d3.event.selection || x2.range();
  x.domain(s.map(x2.invert, x2));
  focus.select(".area").attr("d", area);
  focus.select(".axis--x").call(xAxis);
  svg.select(".zoom").call(zoom.transform, d3.zoomIdentity
      .scale(width / (s[1] - s[0]))
      .translate(-s[0], 0));
}

function zoomed() {
  if (d3.event.sourceEvent && d3.event.sourceEvent.type === "brush") return; // ignore zoom-by-brush
  var t = d3.event.transform;
  x.domain(t.rescaleX(x2).domain());
  focus.select(".area").attr("d", area);
  focus.select(".axis--x").call(xAxis);
  context.select(".brush").call(brush.move, x.range().map(t.invertX, t));
}

function type(d) {
  d.date = parseDate(d.date);
  d.price = +d.price;
  return d;
}
    
    
    
  </script>
</body>

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