D3.js v4 - how to add zoom button with the default

Question

This question covers exactly the same topic as this one already asked and answered:

• D3.js - how to add zoom button with the default wheelmouse zoom behavior

I have also tried to implemented the code that it is in this link http://bl.ocks.org/linssen/7352810.

The reason I am asking here is because the solutions are given using version 3 of D3.js and none of those solve my problem. This is my current implementation regarding the zooming.

let translateVar = [0,0];
let scaleVar = 1;

function create_pan_zoomable_svg() {
    let svg = d3.select("body")
        .append("svg")
        .attr("width", "100%")
        .attr("height", "100%")
        .style("background-color", "#eeeeee")
        .call(_zoom).on("dblclick.zoom", null)
        .append("g");
    d3.select("#zoom_in").on('click', function() { _zoom.scaleBy(svg, 2)});
    d3.select("#zoom_out").on('click', function() { _zoom.scaleBy(svg, 0.5)});

    return svg;
}

var _zoom = d3.zoom()
    .on("zoom", function() {
        translateVar[0] = d3.event.transform.x;
        translateVar[1] = d3.event.transform.y;
        scaleVar = d3.event.transform.k;
        svg.attr('transform', 'translate(' + translateVar[0] + ',' + translateVar[1] + ') scale(' + scaleVar + ')');
    });

I found this post d3.js V4 Button Zoom Implementation acting weird, thinking that it might solve my problem, but adapting the code to mine, turns out that the wheelmouse-based zoom is no longer working and just the buttons. This is the adapted code from such post.

function create_pan_zoomable_svg() {
    let zoom = d3.zoom().on("zoom", zoomed);

    let svg = d3.select("body")
        .append("svg")
        .attr("width", "100%")
        .attr("height", "100%")
        .style("background-color", "#eeeeee")
        .append("g").call(zoom).on("dblclick.zoom", null);

    d3.select("#zoom_in").on("click", function() {
        zoom.scaleBy(svg.transition().duration(750), 1.2);
    });
    d3.select("#zoom_out").on("click", function() {
        zoom.scaleBy(svg.transition().duration(750), 0.8);
    });

    return svg;
}

function zoomed() {
    svg.attr("transform", d3.event.transform);
}

Another problem is that if I were to put the append("g") after calling the zoom both based zooms will work but they will not keep track of the translation.

Please visit for diagnosing the problem: https://jsfiddle.net/vxhuzyp2/5/

Any help would be much appreciated.

Answer 1

Follow the comment and read through the confusion of naming a var svg and and creating an svg element.

let zoom = d3.zoom().on("zoom", zoomed);

let svg = d3.select("svg")
  .attr("width", "100%")
  .attr("height", "100%")
  .style("background-color", "#eeeeee")
  .call(zoom)
  .on("dblclick.zoom", null);
let g = svg.append("g");
//d3.selectAll("#zoom-section i").on("click", zoomClick);
g.append("circle").attr("r", 50).attr("fill", "red");
d3.select("#zoom_in").on("click", function() {
  zoom.scaleBy(svg.transition().duration(750), 1.2);
});
d3.select("#zoom_out").on("click", function() {
  zoom.scaleBy(svg.transition().duration(750), 0.8);
});

function zoomed() {
    g.attr("transform", d3.event.transform);
}

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

<button id="zoom_in">+</button>
<button id="zoom_out">-</button>