Grouped BarChart

This example has a bug that user can interupt the transition even through i add 'end' status at the end of it. Hoping one day i can find out.
The animation is a little uggly because the default animation behavous and my group layout. Whatever.
One thing to be mention, if you chain the selection, transition and on-event, it will not work. I think the chained returned selection is not appropriate for others.

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v3.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>
<div id='container'></div>
<body>
  <script>
var url = 'data.csv'

d3.csv(url, function(error, data){
    
    // major dimension
    var margin = {top: 70, bottom: 40, left: 40, right: 120}, axisPadding = 5;
    var WIDTH = 450, HEIGHT = 300;
    var svgWidth = WIDTH + margin.left + margin.right,
        svgHeight = HEIGHT + margin.top + margin.bottom;
    
    var svg = d3.select('#container')
        .append('svg')
        .attr({width: svgWidth, height: svgHeight});
    var items = d3.keys(data[0]).filter(function(d){ return d !== 'Country'; })
    
    // Country,Electronics,Software,Mechanics
    var nest = d3.nest()
        .key(function(d){ return d.Country; })
        .sortKeys(d3.ascending)
        .rollup(function(leave){
            return items.map(function(e){return {name: e, value: +leave[0][e]}})
        })
        .entries(data);
    var maxIncome = d3.max(nest, function(d0){
        return d3.max(d0.values, function(d1){return d1.value; });
    });
    
    
    // create scales and axises
    var xScale = d3.scale.ordinal()
        .domain(nest.map(function(d){ return d.key; }))
        .rangeBands([0, WIDTH], 0.15);
    var xInner = d3.scale.ordinal()
        .domain(items)
        .rangeBands([0, xScale.rangeBand()], 0);
    var color = d3.scale.category10()
        .domain(items);
    // console.log(xScale.domain())
    var yScale = d3.scale.linear()
        .domain([0, maxIncome])
        .range([0, HEIGHT]);
    
    
    var xAxis = d3.svg.axis()
        .orient('bottom')
        .tickSize(6,0)
        .scale(xScale);
    var yAxis = d3.svg.axis()
        .orient('left')
        .ticks(5)
        .scale(yScale.copy().domain(yScale.domain().slice().reverse()));
    // console.log(yScale.domain());
    
    
    var xGroup = svg.append('g')
        .attr('transform', 'translate(' + 
              [margin.left, margin.top + HEIGHT + axisPadding] + 
              ')');
    xGroup.call(xAxis);
    styleAxis(xGroup);
    
    var yGroup = svg.append('g')
    .attr('transform', 'translate(' +
          [margin.left - axisPadding, margin.top] +
         ')')
    yGroup.call(yAxis);
    styleAxis(yGroup);  
    
    
    // create the body graph
    var mainGroup = svg.append('g')
        .attr('transform', 'translate(' +
              [margin.left, margin.top + HEIGHT] +
              ')');
    var countries = mainGroup.selectAll('g')
        .data(nest)
        .enter()
        .append('g')
        .attr('transform', function(d){
            return 'translate(' + [xScale(d.key), 0] + ')';
        });
    var rects = countries.selectAll('rect')
        .data(function(d){return d.values;})
        .enter()
        .append('rect')
        .each(function(d,i){
            d3.select(this).attr({
                fill: color(d.name),
                x: xInner(d.name),
                y: 0,
                height: yScale(d.value),
                width: xInner.rangeBand(),
            });
        });
    // animation
    rects
        .transition()
        .duration(600)
        .each('end', function(d){
            d3.select(this)
                .transition()
                .attr('y', -yScale(d.value))
        })
        .attr('y', function(d){ return -yScale(d.value); });
    // add interactive behavious
    rects
        .on('mouseover', function(){
            d3.select(this)
                .transition()
                .attr('fill', 'yellow')
        })
        .on('mouseout', function(){
            d3.select(this)
                .transition()
            		.delay(200)
                .attr('fill', function(d){ return color(d.name); })
        });
    // text label
    countries.selectAll('text')
        .data(function(d){return d.values;})
        .enter()
        .append('text')
        .each(function(d,i){
            d3.select(this).text(d.value);
            d3.select(this).attr({
                x: xInner(d.name) + xInner.rangeBand() / 2,
                y: -yScale(d.value) - 3,
                'text-anchor': 'middle',
            });
        });
    
    // create legend
    var legendGroup = svg.append('g')
        .attr('transform', 'translate(' +
              [margin.left + WIDTH + axisPadding, margin.top] +
              ')');
    var legends = legendGroup.selectAll('g')
        .data(items)
        .enter()
        .append('g')
        .attr('transform', function(d,i){return 'translate(' + [0, i * 25] + ')'});
    legends.append('rect')
        .attr({
            fill: function(d){return color(d)},
            rx: 10,
            ry: 10,
            width: 20,
            height: 20,
        });
    legends.append('text')
        .text(function(d){return d;})
        .attr({
            fill: 'black',
            x: 25,
            y: 16,
        });
})

function styleAxis(axis){
    // style path
    axis.select('.domain').attr({
        fill: 'none',
        stroke: '#888',
        'stroke-width': 1
    });
    // style tick
    axis.selectAll('.tick line').attr({
        stroke: '#000',
        'stroke-width': 1,
    })
}

</script>
</body>

https://d3js.org/d3.v3.min.js