ElasticSearch JavaScript Promises

Question

Testing the below in a Mocha/Chain start-up block, the code never waits as expected. Instead, the log reports on the start of creation, then logs from a test (not included), then reports the index creation is complete.

Should not Mocha not exit the before-each block until the Promise is reolved or rejected?

What have I missed?

module.exports.prototype.setup = function (term) {
    this.logger.info("Re-creating the index '%s'", $index);
    return this.client.indices.delete({
        index: $index,
        ignore: [404]
    }).then((err, resp, respcode) => {
        this.logger.info("Creating index '%s'", $index);
        return this.client.indices.create({
            index: $index,
            body: this.schemaBody
        });
    });
};

Promises are not blocking. They are asynchronous not synchronous. — James Lawson
– James Lawson, Commented Jun 24, 2016 at 18:54

Ilia Choly · Accepted Answer · 2016-06-24 18:58:15Z

2

You need to write an async test to test promises.

it("should do something", (done) => {
    setup("stuff").then((index) => {
        /* test index */
        done();
    });
});

You can also return a promise from the test and mocha will wait for it to resolve.

it("should do something", () => {
    return setup("stuff").then((index) => {
        /* test index */
    });
});

answered Jun 24, 2016 at 18:58

Ilia Choly

18.6k14 gold badges95 silver badges166 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

James Lawson · Accepted Answer · 2016-06-24 19:03:32Z

1

How are you calling this code from the Mocha/Chai test? Is it in a beforeEach? From the Mocha Documentation you can do one of the following:

// [Option A] return a promise
beforeEach(() => {
  return setup("foo");
});

// [Option B]: add a `done` parameter, and call it when you are done
beforeEach((done) => {
  return setup("foo").then(() => {
     done();
  });
});

answered Jun 24, 2016 at 19:03

James Lawson

8,69652 silver badges50 bronze badges

5 Comments

Lee Goddard Over a year ago

So often I forget that return statement that I'm surprised I don't check it more thoroughly....! Looked at the code for so long, I could not longer see it, thanks!

James Lawson Over a year ago

Yes it's very easy to forget ... done it many times myself! The return in the first case (Option A) is necessary. The return in the second case should be optional (Option B).

Ilia Choly Over a year ago

@LeeGee this is the part when you choose a right answer and maybe hand out some upvotes ;)

Lee Goddard Over a year ago

Ah! I've been trying to work out how SO works. If the question is good enough to answer, should you not also up-vote it?

Lee Goddard Over a year ago

@JamesLawson — I spent a lot of years with Perl, and its implicit return values. Only now do I miss them....!

Collectives™ on Stack Overflow

ElasticSearch JavaScript Promises

2 Answers 2

Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related