D3 Selection Operators
Selection operators can accept constants or functions.
Function arguments are the current
datum (d) and index (i).
d3.select("body").selectAll("div")
.data([1,2,3])
.enter().append("div")
.attr("class", function(d,i) { return "para"+d; })
.style("font-family", "Gill Sans")
.style("font-size",
function(d,i) { return (16+i)+"pt"; })
.text("Div Text!");