JSFiddle - React, Tailwind, and code Playground

HTML

<div id="result"></div>

JavaScript

var x = '.,2.123,50.0.00.';

var between_dots = x.split('.');
for (var i = 0; i < between_dots.length; i++) {
    between_dots[i] = between_dots[i].replace(/,/g, '.');
}
var y = between_dots.join(',');

document.getElementById('result').innerHTML = y;