JSFiddle - React, Tailwind, and code Playground

CSS

body
{
	font: 16px/18px Arial,Sans-Serif;
}

JavaScript

var center = function (arr) {
    var minX, maxX, minY, maxY;
    for (var i = 0; i < arr.length; i++)
    {
        var x = arr[i][0], y = arr[i][1];
        minX = (x < minX || minX == null) ? x : minX;
        maxX = (x > maxX || maxX == null) ? x : maxX;
        minY = (y < minY || minY == null) ? y : minY;
        maxY = (y > maxY || maxY == null) ? y : maxY;
    }
    return [(minX + maxX) / 2, (minY + maxY) / 2];
};

var getCenter = function(arr)
{
    var x = arr.map(function(a){return a[0]});
    var y = arr.map(function(a){return a[1]});
    var minX = Math.min.apply(null, x);
    var maxX = Math.max.apply(null, x);
    var minY = Math.min.apply(null, y);
    var maxY = Math.max.apply(null, y);
    return [(minX + maxX)/2, (minY + maxY)/2];
};

var getCenter2 = function (arr)
{
	var x = arr.map (x => x[0]);
	var y = arr.map (x => x[1]);
	var cx = (Math.min (...x) + Math.max (...x)) / 2;
	var cy = (Math.min (...y) + Math.max (...y)) / 2;
	return [cx, cy];
}

var log = function (txt)
{
	var p = document.createElement ('p');
	p.appendChild (document.createTextNode (txt));
	document.body.appendChild (p);
}



var coords = [
    [-1.2, 5.1],
    [34.3, 5.2],
    [441.8, 56.9]
];

var c = center(coords);
var d = getCenter(coords);
var e = getCenter2 (coords);
log ("center: " + c);
log ("getCenter: " + d);
log ("getCenter2: " + e);