d3.select(...).datum(...).date is not a function

Using the following piece of code I’m getting the follow error Uncaught TypeError: d3.select(...).datum(...).date is not a function :

         d3.select('#chart_placeholder').datum(data)
                                        .date((d)=>{
                                            return d.data;
                                        }),
                                        .call(eventDropsChart);

or the variation :

         d3.select('#chart_placeholder').datum(data)
                                        .date(function(d){
                                            return d.data;
                                        })
                                        .call(eventDropsChart);

[generall]

According to the demo.js file, date function should be called from eventDropsChart object. So the example in README.md should be changed to something like this:

var eventDropsChart = d3.chart.eventDrops()
  .date(d => d.date);

d3.select('#chart_placeholder')
  .datum(data)
  .call(eventDropsChart);

[JulianoEngineer]

#147