Using "javascript-opentimestamps": "0.4.0"

timestamp-proof.js

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

/** Timestamp text

  {
    text: <Text String>
  }

  @returns via cbk
  {
    [ots]: <OpenTimestamps Base64 Proof String>
  }
*/
module.exports = ({text}, cbk) => {
  if (!text) {
    return cbk(400, 'ExpectedTimestampText');
  }

  const sha = new OpenTimestamps.Ops.OpSHA256();
  const textBuf = Buffer.from(text);

  const detach = OpenTimestamps.DetachedTimestampFile.fromBytes(sha, textBuf);

  OpenTimestamps.stamp(detach)
    .then(() => {
      const fileOts = detach.serializeToBytes();

      return cbk(null, {ots: new Buffer(fileOts).toString('base64')});
    })
    .catch(err => cbk(null, {ots: null}));

  return;
};