For CDN JavaScript URL , you can directly visit on this URL(https://www.srihash.org/) and paste your CDN URL(e.g.https://example.keycdn.com/path/example.js ), It will generate the Hash Key. Need to put the Hash key with append the algo key e.g. integrity=”sha384-xnSV7Ujm6p40d9oLBjPsEZVraTaUO5LOWBOcat4SO3W8JI/jp7QXU5Be9/iy5bfE” crossorigin=”anonymous”, “sha384” is SRI hash key.
For those which is not serving from CDN, in that case you need to download the openssl.
a) Open CMD as administrator mode and come to the path where openssl .exe is placed.
b) Download the required the JS file from that path or create the file.
c) Execute the command :
openssl dgst -sha384 -binary FILENAME.js | openssl base64 -A
Into the cmd at the place where the openssl .exe exist.
Practically Proven 