d3 select existing group code example
Example: append new element for each value in array d3.js
var data = [
["colours", "green", "blue"],
["shapes", "square", "triangle"],
["languages", "javascript", "c++"]
];
var svg = d3.select("body")
.append("svg")
.attr("width", 500)
.attr("height", 200);
var groups = svg.selectAll("groups")
.data(data)
.enter()
.append("g")
.attr("transform", (d, i) => "translate(" + (50 + i * 100) + ",0)");
var texts = groups.selectAll("texts")
.data(d => d)
.enter()
.append("text")
.attr("y", (d, i) => 10 + i * 20)
.text(d => d);