Manually Sortable D3 Barchart

forked from Lulkafe's block: Manually Sortable D3 Barchart

<!DOCTYPE html>
<html lang="en">
<style>
    .axis {
        font: 10px sans-serif;
    }

.axis path,
    .axis line {
        fill: none;
        stroke: #000;
        shape-rendering: crispEdges;
    }
</style>
<head>
    <script src="https://d3js.org/d3.v5.min.js" charset="utf-8"></script>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="vis"></div>

/* Keep at which x coordinate the bar is drawn when the dragging starts */
                bar.property("startX", barX)

/* Since x of the bar starts at the top-left corner of the rect,
                   Here, calculate how much the x of the current bar is apart from the x of the mouse */
                bar.property("xDiff", mouseX - barX);

/* Bring the bar to the front */
                bar.node().parentNode.appendChild(bar.node());

})
            .on("drag", function(){

var curBar = d3.select(this),
                    curIdx = data.indexOf(curBar.datum()),
                    startX = curBar.property("startX"),
                    mouseX = d3.mouse(this)[0],
                    newX = mouseX - curBar.property("xDiff"),
                    xRange = (xScale.range()[1] - xScale.range()[0]) / 2,
                    backlash = xScale.rangeBand() / 2.5,
                    nearestBar, nearestIdx, nearestX;

if (newX < xScale.range()[0] - backlash
                    || xScale.range()[data.length - 1] + backlash < newX)
                    return;

curBar.attr("x", newX);

/* Get the index of the nearest bar */
                if (curIdx == 0)
                    nearestIdx = 1;
                else if (newX < startX || curIdx == data.length - 1)
                    nearestIdx = curIdx - 1;
                else
                    nearestIdx = curIdx + 1;

nearestBar = d3.selectAll(".bar").filter(function(d) { return d == data[nearestIdx]; });
                nearestX = +nearestBar.attr("x");

/* If the current bar is moved close enough to the nearest bar,
                   then update the order of the data array. For example, if we are dragging
                   the first bar and moving to right, the order will be [a, b, c] to [b, a, c] */
                if (startX + xRange < newX || newX < startX - xRange) {

var tmp = data[curIdx];
                    data[curIdx] = data[nearestIdx];
                    data[nearestIdx] = tmp;

curBar.property("startX", nearestX);

xScale.domain(data.map(function(d){ return d.category; }));
                    d3.select(".x.axis").transition().duration(200).call(xAxis.scale(xScale));
                    nearestBar.transition().duration(100).attr("x", xScale(nearestBar.datum().category));
                }

})
            .on("dragend", function(){
                var bar = d3.select(this);
                bar.transition().duration(300).attr("x", xScale(bar.datum().category));
            });

xScale.domain(data.map(function(d){ return d.category; }))
            .rangeRoundBands([ padding.left, width - padding.right], 0.3);
    yScale.domain([0, d3.max(data, function(d) { return d.value; })])
            .range([height - padding.bottom, padding.top]);

xAxis.scale(xScale).orient("bottom");

svg.selectAll("rect").data(data).enter()
            .append("rect").attr("width", xScale.rangeBand())
            .attr("height", function(d) { return height - padding.bottom - yScale(d.value)})
            .attr("x", function(d) { return xScale(d.category); })
            .attr("y", function(d) { return yScale(d.value); })
            .attr("fill", function(d,i) { return color(i); })
            .attr("class", "bar")
            .call(drag);

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

</script>
</body>
</html>

https://d3js.org/d3.v5.min.js