A javascript version of the pseudo code in Chromium's SameSite=None: Known Incompatible Clients https://www.chromium.org/updates/same-site/incompatible-clients

should-send-same-site-none.js

// Copyright 2019 Google LLC.
// SPDX-License-Identifier: Apache-2.0

// Don’t send `SameSite=None` to known incompatible clients.

function shouldSendSameSiteNone() {
  return !isSameSiteNoneIncompatible ();
}

// Classes of browsers known to be incompatible.

function isSameSiteNoneIncompatible(useragent) {
  return hasWebKitSameSiteBug(useragent) 
    || dropsUnrecognizedSameSiteCookies(useragent);
}

function hasWebKitSameSiteBug(useragent) {
  if (isIosVersion(useragent)) return true;

  if (!isMacosxVersion(10, 14, useragent)) return false;

  return isSafari(useragent) 
    || isMacEmbeddedBrowser(useragent);
}

function dropsUnrecognizedSameSiteCookies(useragent) {
  if (isUcBrowser(useragent))
    return !isUcBrowserVersionAtLeast(12, 13, 2, useragent);

  return isChromiumBased(useragent) && 
    isChromiumVersionAtLeast(51, useragent) && 
    !isChromiumVersionAtLeast(67, useragent);
}

// Regex parsing of User-Agent string. (See note above!)

function isIosVersion(major, useragent) {
  var regex = /\(iP.+; CPU .*OS (\d+)[_\d]*.*\) AppleWebKit\//;

  return useragent.matches(regex)[0] == major;
}

function isMacosxVersion(major, minor, useragent) {
  var regex = /\(Macintosh;.*Mac OS X (\d+)_(\d+)[_\d]*.*\) AppleWebKit\//;

  var matches = useragent.matches(regex);

  return matches[0] == major && matches[1] == minor;
}

function isSafari(useragent) {
  var regex = /Version\/.* Safari\//

  return useragent.test(regex) && !isChromiumBased(useragent);
}

function isMacEmbeddedBrowser(useragent) {
  var regex = /^Mozilla\/[\.\d]+ \(Macintosh;.*Mac OS X [_\d]+\) AppleWebKit\/[\.\d]+ \(KHTML, like Gecko\)$/

  return useragent.test(regex);
}

function isChromiumBased (useragent) {
  var regex = /Chrom(e|ium)/;

  return useragent.test(regex);
}

function isChromiumVersionAtLeast(major, useragent) {
  var regex = /Chrom[^ \/]+\/(\d+)[\.\d]* /;

  var version = +useragent.matches(regex)[0];

  return version >= major;
}

function isUcBrowser (useragent) {
  var regex = /UCBrowser\//;

  return useragent.test(regex);
}

function isUcBrowserVersionAtLeast (major, minor, build, useragent) {
  var regex = /UCBrowser\/(\d+)\.(\d+)\.(\d+)[\.\d]*/;

  var matches = useragent.match(regex);

  // // Extract digits from three capturing groups.
  var majorVersion = +matches[0];
  var minorVersion = +matches[0];
  var buildVersion = +matches[0];

  if (majorVersion !== major) 
    return majorVersion > major;

  if (minorVersion != minor)
    return minorVersion > minor;

  return buildVersion >= build;
}