filter brush and zoom line chart

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

.axis--x path {
  display: none;
}

.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}

</style>
<svg width="960" height="500"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var svg = d3.select("svg"),
    margin = {top: 20, right: 80, bottom: 30, left: 50},
    width = svg.attr("width") - margin.left - margin.right,
    height = svg.attr("height") - margin.top - margin.bottom,
    g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var parseTime = d3.timeParse("%Y%m%d");

var x = d3.scaleTime().range([0, width]),
    y = d3.scaleLinear().range([height, 0]),
    z = d3.scaleOrdinal(d3.schemeCategory10);

var line = d3.line()
    .curve(d3.curveBasis)
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.temperature); });

// var area = d3.area()
//     .curve(d3.curveStepAfter)
//     .y0(y(0))
//     .y1(function(d) { return y(d.value); });

// var areaPath = g.append("path")
//     .attr("clip-path", "url(#clip)")
//     .attr("fill", "steelblue");

var yGroup = g.append("g");

var xGroup = g.append("g")
    .attr("transform", "translate(0," + height + ")");

var zoom = d3.zoom()
    .scaleExtent([1 / 4, 8])
    .translateExtent([[-width, -Infinity], [2 * width, Infinity]])
    .on("zoom", zoomed);

var zoomRect = svg.append("rect")
    .attr("width", width)
    .attr("height", height)
    .attr("fill", "none")
    .attr("pointer-events", "all")
    .call(zoom);

g.append("clipPath")
    .attr("id", "clip")
  .append("rect")
    .attr("width", width)
    .attr("height", height);

var xAxis = d3.axisBottom(x);

var yAxis = d3.axisLeft(y);

d3.tsv("data.tsv", type, function(error, data) {
  if (error) throw error;

var cities = data.columns.slice(1).map(function(id) {
    return {
      id: id,
      values: data.map(function(d) {
        return {date: d.date, temperature: d[id]};
      })
    };
  });

console.log(cities);

x.domain(d3.extent(data, function(d) { return d.date; }));

y.domain([
    d3.min(cities, function(c) { return d3.min(c.values, function(d) { return d.temperature; }); }),
    d3.max(cities, function(c) { return d3.max(c.values, function(d) { return d.temperature; }); })
  ]);

z.domain(cities.map(function(c) { return c.id; }));

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

g.append("g")
      .attr("class", "axis axis--y")
      .call(yAxis)
    .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", "0.71em")
      .attr("fill", "#000")
      .text("Temperature, ºF");

var city = g.selectAll(".city")
    .data(cities)
    .enter().append("g")
      .attr("class", "city")
      .attr("id", function(d) { return d.id.substring(0, 3).toUpperCase();});

city.append("path")
      .attr("class", "line")
      .attr("clip-path", "url(#clip)")
      .attr("d", function(d) { return line(d.values); })
      .style("stroke", function(d) { return z(d.id); })
      .attr("id", function(d) { return d.id.substring(0, 3).toUpperCase();});

city.append("text")
      .datum(function(d) { return {id: d.id, value: d.values[d.values.length - 1]}; })
      .attr("transform", function(d) { return "translate(" + x(d.value.date) + "," + y(d.value.temperature) + ")"; })
      .attr("x", 3)
      .attr("dy", "0.35em")
      .style("font", "10px sans-serif")
      .text(function(d) { return d.id; });
  
  var cityLabels = d3.selectAll(".city").selectAll("text");
  
  cityLabels.on("click", function(outer) {
    var me = d3.select(this);
    var on = me.classed("on");
    
    var idSubStr = outer.id.substring(0, 3).toUpperCase();;
    
    if (!on) {
      d3.select("path#" + idSubStr)
        .transition()
     		.style("opacity", 0)
     	 	.on("end", function(d) {
        	d3.select(this).style("visibility", "hidden");
      	});
    }
    else {
      d3.select("path#" + idSubStr)
      	.style("visibility", "visible")
      	.transition()
     		.style("opacity", 1);
    }
    
     me.classed("on", !on);
  });
  
  cityLabels.on("mouseover", function(outer) {
    var me = d3.select(this);
    var on = me.classed("on");
    
    var idSubStr = outer.id.substring(0, 3).toUpperCase();
    
    if (!on) {
    d3.selectAll(".city").selectAll("path")
    	.filter(function(d) {
      	return idSubStr != d.id.substring(0, 3).toUpperCase();;
    	})
    	.transition().style("stroke", "lightgray");
    }
    
    d3.select("g#" + idSubStr).raise();
  });
  
  cityLabels.on("mouseout", function(outer) {
    var me = d3.select(this);
    var on = me.classed("on");
    
    var idSubStr = outer.id.substring(0, 3).toUpperCase();;
    
    d3.selectAll(".city").selectAll("path")
    	.filter(function(d) {
      	return idSubStr != d.id.substring(0, 3).toUpperCase();;
    	})
    	.transition().style("stroke", function(d) { return z(d.id); });
  });

//   var xExtent = d3.extent(data, function(d) { return d.date; });

//   zoom.translateExtent([[x(xExtent[0]), -Infinity], [x(xExtent[1]), Infinity]])
//   y.domain([0, d3.max(cities, function(c) { return (c.values, function(d){ return d.temperature;}); })]);

//   yGroup.call(yAxis).select(".domain").remove();

//   areaPath.datum();

zoomRect.call(zoom.transform, d3.zoomIdentity);

});

function type(d, _, columns) {
  d.date = parseTime(d.date);
  for (var i = 1, n = columns.length, c; i < n; ++i) d[c = columns[i]] = +d[c];
  return d;
}

function zoomed() {
  var xz = d3.event.transform.rescaleX(x);
  xGroup.call(xAxis.scale(xz));
  line.x(function(d) { return xz(d.date);})
  g.selectAll(".line")
    .attr("d", function(d) { return line(d.values); });

//   g.selectAll('.line').style("stroke-width", 2/d3.event.transform.k);

// line.x()
//   g.selectAll(".line")
//     .attr("d", function(d) { return line(d.values); })
//   areaPath.attr("d", area.x(function(d) { return xz(d.date); }));

}

</script>

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