Detect browser TLS compatibility
You can use the API provided by How's my SSL?.
In the following example, I check the tls_version. Checking given_cipher_suites may also be a good idea.
<script>window.parseTLSinfo = function(data) { var version = data.tls_version.split(' '); console.log( version[0] != 'TLS' || version[1] < 1.2 ? 'So bad! Your browser only supports ' + data.tls_version + '. Please upgrade to a browser with TLS 1.2 support.' : 'All OK. Your browser supports ' + data.tls_version + '.' ); console.log(data);};</script><script src="https://www.howsmyssl.com/a/check?callback=parseTLSinfo"></script>
There are at least two web sites that will check the browser capabilities for you, including SSL Labs (https://www.ssllabs.com/ssltest/viewMyClient.html) and HowsMySSL (https://www.howsmyssl.com/). HowsMySSL also has a nice API that can be easily checked from JavaScript.
Here is a wayCreate a image with jQuery, and add a src attribute, I use a button from PayPal, now all the request to PayPal must be via TSL1.2Hope this can work
jQuery('<img />').on({ load: function() { console.log("support TSL1.2"); }, error: function() { console.log('no support TSL1.2'); }}).attr('src','https://www.paypal.com/en_US/i/btn/btn_xpressCheckout.gif');