component.vue

component.js

<script>
import YieldService from '@/services/yieldService'

export default {
  name: 'portfolio-summary',
  props: ['farms'],
  methods: {
    totalArea: function () {
      return this.farms.reduce((a, b) => a + b.areaUsed, 0)
    },
    totalProduced: function () {
      return this.farms.reduce((promisse, farm) => {
        return promisse.then((sum) =>
          return YieldService.get(farm.product, farm.polygon[0][0], farm.polygon[0][1]).then((value) => {
            return sum + farm.areaUsed * value['ton_per_hectare']['avg']
          })
        )
      }, 0)
    }
  }
}
</script>