D3 grouped bar chart: How to rotate the text of x axis ticks?

A reasonable solution can be found here

The result looks like this:

Make sure you fully understand this portion of code:

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    .call(xAxis)
    .selectAll("text")  
    .style("text-anchor", "end")
    .attr("dx", "-.8em")
    .attr("dy", ".15em")
    .attr("transform", "rotate(-65)");

-65 is the angle the label text is rotated, in degrees.

Also, you should increase margin at the bottom, so that the rotated text doesn't get clipped.

WARNING: Rotated text is inevitably rendered by browsers at the end (D3 just creates appropriate svg that is interpreted by browsers), and they do a lousy job rendering rotated text (as opposed to lets say advanced drawing or diagramming software).

Also, related StackOverflow questions:

rotate-x-axis-text-in-d3

how-to-rotate-x-axis-text-in-dimple-js

You might want to consider using D3FC, which has a drop-in replacement for the D3 axis component that supports this feature.

D3FC has an adapter component that will automatically rotate axis labels if they collide:

const axis = fc.axisLabelRotate(fc.axisOrdinalBottom(foodScale));

Here it is in action:

Full disclosure - I am a maintainer and contributor to the D3FC library!