JSFiddle - React, Tailwind, and code Playground

JavaScript

var times= [ '00:00:03.00', '00:00:05.00', '00:00:02.00', '00:00:06.00'],
    date = 0,
    result = '';
function offsetify(t){
    return t < 10 ? '0' + t : t;
}
for(var x = 0; x < times.length; x++ ) {
    var tarr = times[x].split(':');
    date += new Date(0, 0, 0, tarr[0], tarr[1], tarr[2].split('.')[0], tarr[2].split('.')[1]).getTime();   
}
var avg = new Date(date/times.length);
result = offsetify(avg.getHours()) + ':' + offsetify(avg.getMinutes()) + ':' + offsetify(avg.getSeconds()) + '.' + offsetify(avg.getMilliseconds());
document.write(result);