Unable to set angle in transform, rotate using an anom.function

I cannot figure out what is wrong with the following code:

 svg.selectAll(".axislabel")
            .data(featureData)
            .join(
                enter => enter.append("text")
                    .attr("x", d => d.label_coord.x)
                    .attr("y", d => d.label_coord.y)
                    .attr("transform", "rotate(" + (d => d.angle)+ ")" )  //ERROR
                    .text(d => d.name)
            );

I’m getting this error:

Error: <text> attribute transform: Expected number, "rotate(d =u003E d.angle)".

If I use .attr("transform", "rotate(90)" ) then it works.

Thank you

I’ve tried various versions of the syntax.