move to front

JavaScript

d3.selection.prototype.moveToTop = function () {
    return this.each(function () {
        this.parentNode.appendChild(this);
    });
};


var svg = d3.select("body").append("svg");
var data = d3.range(10);

circles = svg.selectAll("circle")
    .data(data)
    .enter()
    .append("circle")
    .attr({
        "r": 50,
        "cx": function (d,i) { return d * 20 + 100},
        "cy": function (d,i) { return d * 20 + 100},
        "fill": "steelblue",
        "stroke": "red"
    })

circles.on("mouseover", function () {
    d3.select(this).moveToTop();
});