Use crypto API to generate a UUID, compliant with RFC4122 version 4.

"use strict";

//
// es6
const uuid = _ =>
  ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
    (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
  );

//
// transpiled
var uuid = function uuid(_) {
    return ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, function(c) {
        return (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16);
    });
};