.env

MODEL_NAME=census
MODEL_VERSION=v1

index.js

// Copyright 2017, Google, Inc.
// Licensed under the Apache License, Version 2.0 (the 'License');
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an 'AS IS' BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

'use strict'

const google = require('googleapis');
const ml = google.ml({
  version: 'v1'
});

// Load environment variables from `.env` file and/or OS.
require('dotenv').config();
const config = {
  modelName: process.env.MODEL_NAME,
  modelVersion: process.env.MODEL_VERSION
}

exports.getPrediction2 = (req, res) => {
  if(req.method === 'POST') {
    // Assume the body contains a JSON object:
    // example: {"age": 25, "workclass": " Private", "education": " 11th", "education_num": 7, "marital_status": " Never-married", "occupation": " Machine-op-inspct", "relationship": " Own-child", "race": " Black", "gender": " Male", "capital_gain": 0, "capital_loss": 0, "hours_per_week": 40, "native_country": " United-States"}
    let data = req.body;

    cmlePredict(data, (err, result) => {
      if(err) {
        // Something went wrong
        console.error(err);
        res.sendStatus(500);
        return;
      }

      // Do something with the result
      res.send(result);
    });
  } else {
    // Only accept POST
    res.sendStatus(400);
  }
};

function cmlePredict(data, callback) {

  // Use the default application credential to authenticate against the ML Engine API
  google.auth.getApplicationDefault(function (err, authClient, projectId) {
    if (err) {
      // Failed to get default credentials (this shouldn't happen)
      console.error(err);
      callback(err);
      return;
    }

    // http://google.github.io/google-api-nodejs-client/21.2.0/ml.html
    const params = {
      auth: authClient,
      name: `projects/${projectId}/models/${config.modelName}/versions/${config.modelVersion}`,
      resource: {
        instances: [
          data
        ]
      }
    };
    // Retrieve a prediction from the given model with the given data array
    ml.projects.predict(params, callback);
  });
}

package.json

{
  "name": "ml-engine-sample",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "dotenv": "^4.0.0",
    "google-auth-library": "^0.12.0",
    "googleapis": "^23.0.0"
  }
}