getBBox by mbostock

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var svg = d3.select("body").append("svg")
    .attr("width", 960)
    .attr("height", 500);

var text = svg.append("text")
    .attr("x", 480)
    .attr("y", 250)
    .attr("dy", ".35em")
    .attr("text-anchor", "middle")
    .style("font", "300 128px Helvetica Neue")
    .text("Hello, getBBox!");

var bbox = text.node().getBBox();

var rect = svg.append("rect")
    .attr("x", bbox.x)
    .attr("y", bbox.y)
    .attr("width", bbox.width)
    .attr("height", bbox.height)
    .style("fill", "#ccc")
    .style("fill-opacity", ".3")
    .style("stroke", "#666")
    .style("stroke-width", "1.5px");

</script>