Brush code for histogram

brush.js

 brush = d3.svg.brush()
                    .x(xScale)
                    .on('brushend', brushend);

                if (dispatch.on('brush')) {
                    svg.append('g')
                        .attr('class', 'brush')
                        .call(brush)
                        .selectAll('rect')
                        .attr('height', height);
                }
  
   function brushend() {
            var selected, start, lastVal, end, selectedRange;

            selected = xScale.domain().filter(function(d) {
                return (brush.extent()[0] <= xScale(d)) && (xScale(d) <= brush.extent()[1]);
            });

            start = selected[0];
            lastVal = selected.length - 1;
            end = selected[lastVal];
            selectedRange = [start, end];

            return brush.extent()[0] instanceof Date ?
                dispatch.brush({
                    range: brush.extent(),
                    config: args,
                    e: d3.event,
                    data: latestData,
                }) :
                dispatch.brush({
                    range: selectedRange,
                    config: args,
                    e: d3.event,
                    data: latestData,
                });
        }