select.js

d3.selectAll("circle.a").style("fill", "red")
// select every circle with class "a" and fill it red.

d3.select("circle").style("fill") // => "red"
// Note that calling .style without the second argument will 
// return the current value.

d3.select("circle").remove() // delete the circle

d3.selectAll(“div.sales”).data([1,5,11,3])
// binds the elements in the array [1,5,11,3] to <div> elements with the class "sales"