JSFiddle - React, Tailwind, and code Playground

JavaScript

function f(txt) {
    this.toNum = function(n) {
        return parseInt(n, 10);
    };

    return txt.split(",").reduce(function(a, b) {
        var aa = a.split('.').map(this.toNum); //call .map to convert string to integer
        var bb = b.split('.').map(this.toNum);

        for (var i = 0; i < aa.length; i++) {
            if (aa[i] == bb[i])
                continue;

            if (aa[i] > bb[i])
                return a;
            else
                return b;

            if (bb.length < i)
                return a;
        };

        if (bb.length > aa.length)
            return b;
    });
}

alert(f("8.4, 1.1.1.1.1.1.1.1.1.1.1, 133.1.1.33, 133.1.2, 7.9"));
alert(f("8.0, 8.0.1"));
alert(f("90,88,89"));