API CURL Get Document _id by Query Match

Note: Upon further research, I have reduced this question to a more specific inquiry.

Objective is to fetch a document _id by matching a field in a Javascript / Node.js application that leverages the Get API and CURL. Let's assume that no more than one document _id will match the field ("email" in this example).

Step 1 - Query for the document based on email.
I'm familiar with how to run the query via Sense.

GET /users/user/_search
  "query": {
    "match": {
      "email": "foo@bar.com"

I believe this would look like something like this if using the API and CURL in a custom JavaScript / Node.js application based on an example from Elastic | Search, this seems very lightweight:

curl -XGET 'http://localhost:9200/users/user/_search?q=email:'foo@bar.com''

Or is there a signficant advantage to using Elasticsearch.js like this (Note: I've omitted the 'require' statements and client setup from the discussion here but that is well covered in the Elasticsearch.js link)?:

  index: 'users',
  type: 'user',
  body: {
    query: {
      match: {
        email: userEmail
}).then(function (resp) {
  var hits = resp.hits.hits;
}, function (err) {

Step 2 - Return the document _id value as a string in the JavaScript / Node.js application for use

This is where I have seen few examples and could use some guidance. If using the elasticsearch.js example, perhaps the next step is to do a regex on hits to capture the value that follows '_id:'? Or is there a member of 'resp.hits.hits' that can return the _id(s)?

Is _id a member of resp.hits.hits (aka hits). Can I access the _id as hits._id?