Example of getBBox()

CSS

svg {
    background-color: linen;
}

JavaScript

var svg = d3.select("body").append("svg").attr('width',600).attr('height',100);

var text = svg.append("text")
    .attr("x",10)
    .attr("y",20)
    .text("hello there from Nivaldo who is current living in Va Beach");

var rect = svg.append("rect")
    .attr(text.node().getBBox())
    .style("fill","red")
    .style("opacity",0.5);
    
console.log(text.node().getBBox());