d3js v4 map + zoom + mark city + drag

By Heber Almeida (http://www.heberonline.com.br) Built with blockbuilder.org

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
   <script>
        const width = 960,
            height = 500,
            projection = d3.geoMercator()
                .center([0, 5])
                .scale(200)
                .rotate([-180, 0]),
            svg = d3.select('body').append('svg')
                .attr('width', width)
                .attr('height', height),
            path = d3.geoPath()
                .projection(projection),
            g = svg.append('g'),
            cities = [{ 'code': 'OTT', 'city': 'OTTAWA', 'country': 'CANADA', 'lat': '23.10', 'lon': '120.34' }, { 'code': 'BSB', 'city': 'BRASILIA', 'country': 'BRAZIL', 'lat': '-32.85', 'lon': '133.30' }, { 'code': 'DEL', 'city': 'DELHI', 'country': 'INDIA', 'lat': '4.71', 'lon': '-127.57' }, { 'code': 'CMX', 'city': 'CIDADE DO MÉXICO', 'country': 'MÉXICO', 'lat': '0.42', 'lon': '93.19' }, { 'code': 'SID', 'city': 'SIDNEY', 'country': 'AUSTRALIA', 'lat': '-48.38', 'lon': '-71.71' }, { 'code': 'TOK', 'city': 'TOQUIO', 'country': 'JAPÃO', 'lat': '17.34', 'lon': '-81.73' }, { 'code': 'CCA', 'city': 'CIDADE DO CABO', 'country': 'AFRICA DO SUL', 'lat': '-43.20', 'lon': '-171.97' }, { 'code': 'CMP', 'city': 'CAMPO GRANDE', 'country': 'BRASIL', 'lat': '-36.15', 'lon': '130.72' }, { 'code': 'PAR', 'city': 'PARIS', 'country': 'FRANÇA', 'lat': '22.19', 'lon': '174.27' }, { 'code': 'NOY', 'city': 'NOVA YORK', 'country': 'USA', 'lat': '11.23', 'lon': '112.96' }]

g.append('image')
            .attr('xlink:href', 'https://upload.wikimedia.org/wikipedia/commons/8/80/World_map_-_low_resolution.svg')
            .append('path')
            .attr('d', path)

// Carregar cidades | load city
        //d3.json('cities.json', (error, data) => {
        const circles = g.selectAll('circle')
            .data(cities)
            .enter()
            .append('a')
            .attr('xlink:href', d => `https://www.google.com/search?q=${d.city}`
            )
            .append('circle')
            .attr('cx', d => projection([d.lon, d.lat])[0])
            .attr('cy', d => projection([d.lon, d.lat])[1])
            .attr('r', 5)
            .style('fill', 'red'),
            drag_handler = d3.drag()
                .on('start', drag_start)
                .on('drag', drag_drag)

function drag_start() {
            start_x = +d3.event.x
            start_y = +d3.event.y
        }

function drag_drag(d) {
            //Get the current scale of the circle 
            //case where we haven't scaled the circle yet
            // get lon x lat
            console.log('lon x lat', projection.invert([d3.event.x, d3.event.y]))

d3.select(this)
              .attr('cx', d.x = d3.event.x).attr('cy', d.y = d3.event.y)
        }

drag_handler(circles)

// zoom and pan
        const zoom = d3.zoom()
            .on('zoom', () => {
                g.style('stroke-width', `${1.5 / d3.event.transform.k}px`)
                g.attr('transform', d3.event.transform) // updated for d3 v4
            })

svg.call(zoom)
    </script>
</body>

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