level-majority-map-reduce.js

const User = require('../../app/models/user');

module.exports = function() {
  const query = {
    topics: { $exists: true},
    'onboardingSteps.0': 'revision',
  }

  /* eslint-disable */
  const o = {},
    self = this;

  o.query = query;
  o.verbose = true;
  // o.limit = 500;

  o.map = function() {

    function extractLevelMajority (topicsArray) {

      const BEGINNER_ID = '578cb033c774cd4d3949b82a';
      const BASIC_ID = '554373512de2f98af6ea5bc6';
      const MEDIUM_ID = '554373512de2f98af6ea5bd0';
      const EXPERT_ID = '554373512de2f98af6ea5bcc';

      let beginner = 0;
      let basic = 0;
      let medium = 0;
      let expert = 0;

      topicsArray.map(l => l.valueOf()).forEach(levelId => {
        if (levelId === BEGINNER_ID) {
          beginner += 1;
        } else if (levelId === BASIC_ID) {
          basic += 1;
        } else if (levelId === MEDIUM_ID) {
          medium += 1;
        } else if (levelId === EXPERT_ID) {
          expert += 1;
        }
      })

      // console.log(beginner, basic, medium, expert);

      if (beginner > basic && beginner > medium && beginner > expert) {
        return 'beginner';
      } else if (basic > beginner && basic > medium &&  basic > expert) {
        return 'basic';
      } else if (medium > beginner && medium > basic && medium > expert) {
        return 'medium';
      } else if (expert > beginner && expert > medium && expert > basic) {
        return 'expert';
      }
      return 'no-majority';
    }
    const label = extractLevelMajority(this.topics.map(t => t.levelId || '').filter(Boolean));
    emit(this._id, label);

  }

  /* eslint-enable */

  User.mapReduce(o, (err, results) => {
    if (err) throw err;
    const r = results.reduce((acc, val) => {
      acc[val.value] = acc[val.value] + 1 || 1;
      return acc;
    }, {});
    
    console.log(r);
    process.exit(0);
  })

}