A small Express servlet to work out shipping costs!

shipment-costs-express-server.js

var express = require('express');
// Helper libraries are supplied if needed
// const _ = require('lodash')
// const r = require('ramda')
const router = express.Router()

// Same state uses the base rate on the weight;
// Different state shipments have a fixed 20% cost increase on top of the previous value (rate on weight);
// Packages can have distinct weight units, either pounds or kilograms.
// Weight needs to be validated on pounds, thus requiring conversion from kg;
// Weight rate is tiered:
// Shipments up to 2 pounds are free;
// When pounds are > 2, each pound will be 1 dollar;
// When pounds are > 20, each pound will be 2 dollars;
// Examples:
// 1 pound shipment will be free;
// 3 pound shipment will be 3 dollars;
// 8 pound shipment will be 8 dollars;
// 25 pound shipment will be 50 dollars;

router.post('/request-shipment', function (req, res, next) {
	// TODO implement based on README

	const shipmentRequest = req.body;
	console.log(`shipmentRequest object is: ${JSON.stringify(shipmentRequest)}`);

	const sameStatePackage = shipmentRequest.shippingAddress.state === shipmentRequest.receivingAddress.state;

	// Iterate packages
	let overallCost = 0;
	let overallWeight = 0;

	shipmentRequest.packages.forEach(parcel => {
		if (parcel.unit === 'KG') {
			// Then convert weight to LB
			// 1 KG = 2.2 LB
			parcel.weight = Math.round(((parcel.weight * 2.2) * 100 / 100));
		}

		overallWeight += parcel.weight;
	});

		// Check unit of measurement for weight
	if (overallWeight > 2 && overallWeight < 20) {
		if (!sameStatePackage) {
			overallCost += outerStatePackageCost(overallWeight);
		} else {
			overallCost += overallWeight;
		}
	} else if (overallWeight > 20) { // be explicit and declarative for readibility
		const currentParcelCost = overallWeight * 2;
		if (!sameStatePackage) {
			overallCost = outerStatePackageCost(currentParcelCost);
		} else {
			overallCost += currentParcelCost;
		}
	}

	return res.status(200).send({ shipment: { cost: overallCost } });
});

const outerStatePackageCost = originalCost => originalCost * 1.2;

module.exports = router;

const exampleShippingCostsToCalculate = {
  "valid_shipment_request_free_same_state": {
    "shipment_request": {
      "shippingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "receivingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "packages": [
        {
          "name": "Small package",
          "weight": 1,
          "unit": "LB"
        }
      ]
    },
    "shipment": {
      "cost": 0
    }
  },
  "valid_shipment_request_free_different_state": {
    "shipment_request": {
      "shippingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "receivingAddress": {
        "addressName": "856 S. Cross St.",
        "state": "CT",
        "name": "John"
      },
      "packages": [
        {
          "name": "Small package",
          "weight": 1,
          "unit": "LB"
        }
      ]
    },
    "shipment": {
      "cost": 0
    }
  },
  "valid_shipment_request_cheap_same_state": {
    "shipment_request": {
      "shippingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "receivingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "packages": [
        {
          "name": "Small package",
          "weight": 1,
          "unit": "LB"
        },
        {
          "name": "Macbook Pro",
          "weight": 4,
          "unit": "LB"
        }
      ]
    },
    "shipment": {
      "cost": 5
    }
  },
  "valid_shipment_request_cheap_different_state": {
    "shipment_request": {
      "shippingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "receivingAddress": {
        "addressName": "856 S. Cross St.",
        "state": "CT",
        "name": "John"
      },
      "packages": [
        {
          "name": "Small package",
          "weight": 1,
          "unit": "LB"
        },
        {
          "name": "Macbook Pro",
          "weight": 4,
          "unit": "LB"
        }
      ]
    },
    "shipment": {
      "cost": 6
    }
  },
  "valid_shipment_request_expensive_same_state": {
    "shipment_request": {
      "shippingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "receivingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "packages": [
        {
          "name": "Big TV",
          "weight": 23,
          "unit": "LB"
        },
        {
          "name": "Macbook Pro",
          "weight": 4,
          "unit": "LB"
        }
      ]
    },
    "shipment": {
      "cost": 54
    }
  },
  "valid_shipment_request_expensive_different_state": {
    "shipment_request": {
      "shippingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "receivingAddress": {
        "addressName": "856 S. Cross St.",
        "state": "CT",
        "name": "John"
      },
      "packages": [
        {
          "name": "Big TV",
          "weight": 23,
          "unit": "LB"
        },
        {
          "name": "Macbook Pro",
          "weight": 4,
          "unit": "LB"
        }
      ]
    },
    "shipment": {
      "cost": 64.8
    }
  },
  "valid_shipment_request_mixed_weight_units": {
    "shipment_request": {
      "shippingAddress": {
        "addressName": "7433 Victoria Ave.",
        "state": "WI",
        "name": "Jones"
      },
      "receivingAddress": {
        "addressName": "856 S. Cross St.",
        "state": "CT",
        "name": "John"
      },
      "packages": [
        {
          "name": "Big TV",
          "weight": 10.432636917,
          "unit": "KG"
        },
        {
          "name": "Macbook Pro",
          "weight": 4,
          "unit": "LB"
        }
      ]
    },
    "shipment": {
      "cost": 64.8
    }
  }
}