A few years ago it was said that update() and digest() were legacy methods and the new streaming API approach was introduced. Now the docs say that either method can be used. For example:
var crypto = require('crypto');
var text = 'I love cupcakes';
var secret = 'abcdeg'; //make this your secret!!
var algorithm = 'sha1'; //consider using sha256
var hash, hmac;
// Method 1 - Writing to a stream
hmac = crypto.createHmac(algorithm, secret);
hmac.write(text); // write in to the stream
hmac.end(); // can't read from the stream until you call end()
hash = hmac.read().toString('hex'); // read out hmac digest
console.log("Method 1: ", hash);
// Method 2 - Using update and digest:
hmac = crypto.createHmac(algorithm, secret);
hmac.update(text);
hash = hmac.digest('hex');
console.log("Method 2: ", hash);
Tested on node v6.2.2 and v7.7.2
See https://nodejs.org/api/crypto.html#crypto_class_hmac. Gives more examples for using the streaming approach.