final vector

<!DOCTYPE html>
<meta charset="utf-8">
<title>Class 10</title>
<style>
body {
  margin: 0;
}
path {
  fill: none;
  stroke: red;
  stroke-linejoin: round;
  stroke-width: 1.5px;
}
.info {
  color: #000;
  position: absolute;
  background-color: rgba(200, 200, 200, .7);
  visibility: hidden;
  padding: 0.5em;
  bottom: 100px;
  right: 100px;
}
/* This style is used when dragging the dot */
.active {
  stroke: #000;
  stroke-width: 2px;
}
</style>
<svg></svg>
<div class='info'></div>
<script src="//d3js.org/d3.v4.min.js"></script>
<script src="//d3js.org/d3-tile.v0.0.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
// 1. NEW: Define an array with Washington DC longitude & latitude
var dc = [-77.0369, 38.9072];
// 2. NEW: Add an HTML <div> element that will function as the tooltip
var tooltip = d3.select('body').append('div')
    .attr('class', 'tooltip')
    .text('Hello, world!')
var pi = Math.PI,
    tau = 2 * pi;
var width = Math.max(960, window.innerWidth),
    height = Math.max(500, window.innerHeight);
// Initialize the projection to fit the world in a 1×1 square centered at the origin.
var projection = d3.geoMercator()
    .scale(1 / tau)
    .translate([0, 0]);
var path = d3.geoPath()
    .projection(projection);
var tile = d3.tile()
    .size([width, height]);
var zoom = d3.zoom()
    .scaleExtent([1 << 11, 1 << 18])
    .on("zoom", zoomed);
var svg = d3.select("svg")
    .attr("width", width)
    .attr("height", height);
var raster = svg.append("g");
var vector = svg.append("path");
var data; // This is a global variable
var counties = "https://raw.githubusercontent.com/AnaMal08/classes/master/Class14/counties.json";
var usgs = "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_week.geojson";
d3.queue()
    .defer(d3.json, counties)
    .await(ready);
function ready(error, counties) {
  if (error) throw error;
  data = counties;
  console.log("this is data", data)
  vector
      .datum(topojson.mesh(counties, counties.objects.counties));
  // Compute the projected initial center.
  var center = projection([-98.5, 39.5]);
  // Apply a zoom transform equivalent to projection.{scale,translate,center}.
  svg
      .on('mousemove', mousemoved)
      .on('mouseout', function() { d3.select('.info').style('visibility', 'hidden') })
      .call(zoom)
      .call(zoom.transform, d3.zoomIdentity
          .translate(width / 2, height / 2)
          .scale(1 << 12)
          .translate(-center[0], -center[1]));
  var layer1 = svg.append("g");
  var layer2 = svg.append("g");
     // 3. NEW: Add a draggable circle to the map
  // See: https://bl.ocks.org/mbostock/22994cc97fefaeede0d861e6815a847e)
  layer2.append("circle")
      .attr("class", "dc")
      .attr("cx", projection(dc)[0])
      .attr("cy", projection(dc)[1])
      .attr("r", 10)
      .style("fill", "yellow")  // Make the dot yellow
      .call(d3.drag()           // Add the drag behavior
        .on("start", dragstarted)
        .on("drag", dragged)
        .on("end", dragended));
  // NEW: The following 3 functions define what happens during drag events
// See https://bl.ocks.org/mbostock/22994cc97fefaeede0d861e6815a847e for a simpler d3-drag demo
function dragstarted(d) {
  // Highlight the circle that's being dragged
  d3.select(this).classed("active", true);
  // Make the tooltip visible during drag events
  tooltip.style("visibility", "visible");
}
function dragged(d) {
  // Reposition the circle to follow the mouse during drag
  d3.select(this).attr("cx", d3.event.x).attr("cy", d3.event.y);
  // Reposition the tooltip too
  tooltip.style("left", (d3.event.x - 10) + "px").style("top", (d3.event.y - 10) + "px");
  // Add the name of the state to the tooltip
  layer1.selectAll('path')
      .filter(function(d) { return d3.geoContains(d, projection.invert([d3.event.x, d3.event.y])) })
      .each(function(d) { tooltip.html(d.properties.name); })
}
function dragended(d) {
  // Eliminate the highlight when dragging ends
  d3.select(this).classed("active", false);
  // Hide the tooltip
  tooltip.style("visibility", "hidden");
}
}
function zoomed() {
  var transform = d3.event.transform;
  var tiles = tile
      .scale(transform.k)
      .translate([transform.x, transform.y])
      ();
  projection
      .scale(transform.k / tau)
      .translate([transform.x, transform.y]);
  vector
      .attr("d", path);
  var image = raster
      .attr("transform", stringify(tiles.scale, tiles.translate))
    .selectAll("image")
    .data(tiles, function(d) { return d; });
  image.exit().remove();
  image.enter().append("image")
      .attr("xlink:href", function(d) { return "https://" + "abc"[d[1] % 3] + ".tile.openstreetmap.org/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; })
      .attr("x", function(d) { return d[0] * 256; })
      .attr("y", function(d) { return d[1] * 256; })
      .attr("width", 256)
      .attr("height", 256);
}
function stringify(scale, translate) {
  var k = scale / 256, r = scale % 1 ? Number : Math.round;
  return "translate(" + r(translate[0] * scale) + "," + r(translate[1] * scale) + ") scale(" + k + ")";
}
function mousemoved() {
  d3.select('.info')
      .style('visibility', 'visible')
      .text(formatLocation(projection.invert(d3.mouse(this)), projection.scale()));
}
function formatLocation(p, k) {
  var format = d3.format("." + Math.floor(Math.log(k) / 2 - 2) + "f");
  return (p[1] < 0 ? format(-p[1]) + "°S" : format(p[1]) + "°N") + " "
       + (p[0] < 0 ? format(-p[0]) + "°W" : format(p[0]) + "°E");
}
</script>

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

https://d3js.org/d3-tile.v0.0.min.js

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