backendless-coderunner/examples/handlers/custom/average-stars.js

Backendless CodeRunner for Node.js

'use strict'

/***
 * This is an example of custom event handler which accepts a string 'movie' parameter,
 * and, using the Backendless SDK, retrieves the 'Review' table data,
 * calculates the average star rating for the passed movie and returns it to the caller
 */

Backendless.ServerCode.customEvent('movieRating', request => {
  const movie = request.args.movie
  const query = {
    condition: `movie = '${movie}'`
  }

  return Backendless.Data.of('Review').find(query).then(
    reviews => {
      const totalReviews = reviews.data.length
      const totalStars = reviews.data.reduce((memo, review) => memo + review.stars, 0)

      // use console to debug your server code
      console.log(`${totalReviews} reviews found with ${totalStars} stars in total`)

      if (totalReviews === 0) {
        throw new Error(`No reviews found for [${movie}] movie`)
      }

      return totalStars / totalReviews
    },

    err => {
      console.error(err)

      throw new Error('Movie lookup failed')
    }
  )
})