Q:

how to compute the size of polygon in svg by d3.js

This is a polygon in my svg file.
<polygon id="UKCYEW" fill="#09252E" points="840.218,415.85 696.468,415.85 696.468,373.974 817.176,373.558 "/>

Through D3.js I can get all the points in the polygon and get the center of this polygon
var points = d3.select('#'+name).attr('points');
    if(points !=null){
        var temps = [], posx = 0, posy = 0;
        temps = points.split(' ');
        //console.log('.................................. temperary positions',temps);
        temps.forEach(function(e){
            // console.log(e);
            var arr = e.split(',');
        posx += Number(arr[0]), posy +=Number(arr[1]);
    })
    posx = posx/temps.length , posy = posy/temps.length;
}                               

now the point for me, is how to compute the size of polygon 

A:

document.getElementById("UKCYEW")[0].getBBox() will get the x, y, width and height. The size is the width and height and the centre is x + width / 2, y + height / 2. Isn't that simpler?

