[JavaScript] How to calculate and encode an element digest.

calculate_element_digest.js

/*
 * The following snippet uses the Forge JavaScript library (https://github.com/digitalbazaar/forge)
 * to calculate the SHA512 digest hash of the received element and return it as a BASE64
 * encode String. It is used to calculate the digest of the content of the request and it
 * is an important element of the signature. The expected parameter is the plain text
 * representation of the request's body being sent. For SOAP, it is the XML node being signed.
 * For RESTful is the JSON document beingin sent. For more information about how to use the
 * Forge JavaScript library, please, refer to the aforementioned URL.
 *
 * Gists provided for illustrative purposes only. Developers can use these as a support tool
 * but the Office of the Revenue Commissioners (Revenue) does not provide any warranty with 
 * these gists. 
 */
function calculateAndEncodeElementDigest(element) {
    return forge.util.encode64(
        forge.md.sha512
            .create()
            .update(element)
            .digest()
            .getBytes()
    );
}