ESRI ArcGIS Vue Mixin

esriFunctions.js

import {
  loadScript,
  loadModules
} from 'esri-loader'

// preload the ArcGIS API
const options = {
  url: '//js.arcgis.com/3.27/',
}

loadScript(options)

export default {
  data () {
    return {
      esri: {},
      // esriModules are called by the parent component to be included
      // at the time of mixin use within a component
      esriModules: []
    }
  },
  created () {
    // These are the base modules required to use an ESRI map with this mixin
    let modules = [
      'esri/map',
      'esri/symbols/SimpleMarkerSymbol',
      'esri/symbols/SimpleLineSymbol',
      'esri/Color',
      'esri/graphic'
    ]
    // Iterate the loaded modules to create them as sublcasses of this.esri
    // using the last part of their prototype declared class name
    let declaredClass
    loadedModules.forEach((loadedModule, i) => {
      if (loadedModule.prototype) {
        declaredClass = loadedModule.prototype.declaredClass
        this.esri[declaredClass.substring(declaredClass.lastIndexOf('.') + 1)] =
        loadedModule
      } else {
        this.esri[modules[i].substring(modules[i].lastIndexOf('/') + 1)] = loadedModule
      }
    })

    loadModules(modules)
      .then(loadedModules => {
        // Iterate the loaded modules to create them as sublcasses of this.esri
        // using the last part of their prototype declared class name
        let declaredClass
        loadedModules.forEach(loadedModule => {
          declaredClass = loadedModule.prototype.declaredClass
          this.esri[declaredClass.substring(declaredClass.lastIndexOf('.') + 1)] =
            loadedModule
        })

        // Create the map 
        this.map = new this.esri.Map(this.$refs.map, {
          basemap: 'topo',
          zoom: 17
        })

        this.map.on('load', () => {
          console.log('Map loaded') // eslint-disable-line no-console
          this.onMapLoaded()
        })

        this.map.on('click', (e) => {
          this.map.graphics.clear() // Remove any user clicked graphics
          // Now add a symbol to show where we clicked
          let pointSymbol = new this.esri.SimpleMarkerSymbol(
            this.esri.SimpleMarkerSymbol.STYLE_CROSS, 22,
            new this.esri.SimpleLineSymbol(this.esri.SimpleLineSymbol.STYLE_SOLID,
              new this.esri.Color([0, 0, 0]), 4)
          )
          let clickPointGraphic = new this.esri.Graphic(e.mapPoint, pointSymbol)
          this.map.graphics.add(clickPointGraphic)

          this.onMapClicked(e)
        })

      }).then(() => {
        this.onModulesLoaded()
      })
      .catch(err => {
        console.error(err) // eslint-disable-line no-console
      })
  },
  methods: {
    /**
     * onMapClicked fired when the map is clicked
     * @param  event e  Map click event
     * @return void
     */
    onMapClicked (e) {
      // Mixin function that can be overridden in the parent component
    },
    /**
     * onMapLoaded fired when the map is loaded
     * @return void
     */
    onMapLoaded () {
      // Mixin function that can be overridden in the parent component
    },
    /**
     * onModulesLoaded fire when all ESRI modules have been loaded
     * @return void
     */
    onModulesLoaded () {
      // Mixin function that can be overridden in the parent component
    }
  }
}

Quick question about the module loading, the part in lines 31-42 is almost the same(the if clause is missing) as in 46-53. What purpose does it serve?