OTS-info.js

const OpenTimestamps = require('javascript-opentimestamps');
var fs = require('fs');

fs.readFile('bitcoin.pdf.ots', 'utf8', (err, contents) => {
    const fileOts = Buffer.from(contents.toString('utf8'));
    const detached = OpenTimestamps.DetachedTimestampFile.deserialize(fileOts);
    const infoResult = OpenTimestamps.info(detached);
    console.log(infoResult)
});

fs.readFile('hello-world.txt.ots', 'utf8', (err, ots) => {
    const infoResult = OpenTimestamps.info(ots);
    console.log(infoResult)
});

I'm using the javascript library at https://github.com/opentimestamps/javascript-opentimestamps.
I've tried the examples at README.md and the one in the examples/ folder:

1. Example in examples/test.js:

$ node examples/test.js
STAMP
INFO
err=TypeError: Cannot read property '_HASHLIB_NAME' of undefined
(node:37926) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): Invalid input
(node:37926) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

2. Example running the code in this gist:

$ node info.js 
Unknown operation tag:  ef
/Users/federicoulfo/bauso/notarizza-function-docs-uploader/functions/node_modules/javascript-opentimestamps/src/timestamp.js:63
        const result = op.call(initialMsg);
                         ^

TypeError: Cannot read property 'call' of undefined
    at doTagOrAttestation (/Users/federicoulfo/bauso/notarizza-function-docs-uploader/functions/node_modules/javascript-opentimestamps/src/timestamp.js:63:26)
    at Function.deserialize (/Users/federicoulfo/bauso/notarizza-function-docs-uploader/functions/node_modules/javascript-opentimestamps/src/timestamp.js:77:5)
    at Function.deserialize (/Users/federicoulfo/bauso/notarizza-function-docs-uploader/functions/node_modules/javascript-opentimestamps/src/detached-timestamp-file.js:96:33)
    at fs.readFile (/Users/federicoulfo/bauso/notarizza-function-docs-uploader/functions/info.js:6:59)
    at tryToString (fs.js:449:3)
    at FSReqWrap.readFileAfterClose [as oncomplete] (fs.js:436:12)