d3.voronoi mutates data

[DDDgfx]

Like some d3 layouts and functions. Voronoi seems to mutate data, but unlike some others (force for example adds properties but does not move them), all properties are dropped into a data node, and an array of 4 points is left at top level. As a result, it seems, I am unable to access the data properties to use a key function when joining when attempting to extend this example to apply animations with the general update pattern.
https://bl.ocks.org/mbostock/6526445e2b44303eebf21da3b6627320

Likewise, I am unable to to generate voronoi diagram without changing the data used elsewhere in my project. Which I think would be helpful as the voronoi is only being used in one state of my data display. Would it be preferable if it did not mutate, or am I missing something?

[mbostock]

d3.voronoi does not mutate the input data. Internally, it wraps each element in the input data array in a new object called a site (a two-element array [x, y]). The site also stores a reference to the original data element as the data property.

d3-voronoi/src/voronoi.js

Lines 10 to 17 in c59798a

	function voronoi(data) {
	return new Diagram(data.map(function(d, i) {
	var s = [Math.round(x(d, i, data) / epsilon) * epsilon, Math.round(y(d, i, data) / epsilon) * epsilon];
	s.index = i;
	s.data = d;
	return s;
	}), extent);
	}

Some of the voronoi methods expose the site objects. Others return the original elements from the input data array, such as voronoi.triangles.

[DDDgfx]

For some reason, I was seeing these site arrays, and the data object when I logged my original data. Also was experiencing this:

    var cells = dataLr.selectAll(".data-bub").data(d3.voronoi()
            .extent([
                [-100, -100],
                [svgWidth, svgHeight]
            ])
            .x(function(d) {
                //console.log(d);
                return d.x;
            })
            .y(function(d) {
                return d.y;
            })
            .polygons(fData),
            function(d) {
                console.log(d); //my properties are logged
                console(d.data.id); //the property itself returns undefined
            })
        .enter().append("g");

But now I'm not seeing that, and I have decided not to try to key the diagram. Thank you for explainig.

[DDDgfx]

Overall, trying to learn what d3 modules do to my data by logging it to the console seems to be a very bad idea as the console is logging the end state no matter where in the code the command is.