How to assign random colors to D3 bar chart?

Question

I am working on a D3 bar chart as per the mock-up below:

How do I make the bars to have rando

Answer 1

colors = d3.scale.category20()

rects = svg.selectAll('rect')
                .data(data)
                .enter()
                .append("rect")
                .attr("class","rect")
                .....#other attributes
                .attr("fill",function(d,i){return colors(i)})