How to add sum of same objects using lodash

Question

I am new to development.

I want to group the same objects inside array of json objects. E.g. here is my JSON array:

var data = [
    {
        zone: "Bottom",
        group: "Bottom girders",
        original: 7,
        gauge: 3,
        dPercent: 0,
        permissible: 10,
    },
    {
        zone: "Bottom",
        group: "Bottom girders",
        original: 9,
        gauge: 7,
        dPercent: 0,
        permissible: 10,
    },
    {
        zone: "Bottom",
        group: "risers",
        original: 7,
        gauge: 3,
        dPercent: 0,
        permissible: 10,
    },
    {
        zone: "Neutral axis",
        group: "Transverse PSM",
        original: 17,
        gauge: 28,
        dPercent: 0,
        permissible: 15,
    },
    {
        zone: "Neutral axis",
        group: "Transverse PSM",
        original: 17,
        gauge: 12,
        dPercent: 0,
        permissible: 15,
    },
];

The final output I expect is:

[
      {
        "zone": "Neutral Axis",
        "groups": [
           { "zone":"Bottom", "group":"Bottom girders","original": 34, "gauge": 40, "dPercent": 5.3, "permissible": 10 }
        ]
      },
      {
        "zone": "Bottom",
        "groups": [
           { "zone":"Bottom", "group":"Bottom girders", "original": 16, "gauge": 10, "dPercent": 5.3, "permissible": 10 },
           { "zone":"Bottom", "group":"risers", "original": 7, "gauge": 3, "dPercent": 5.3, "permissible": 10 }
        ]
      }
    ]

Logic: I want to club data zone wise first then each zone having different group and based on group i want to add original and gauge values final output as shown

Here is my code link i have tried https://angular-ivy-zm5kqo.stackblitz.io

Thank you so much in Advance !

Answer 1

From your output example I suppose that you want group your entities by their zone property, and get result as an array.

The code that do it:

var data = [/*your data here*/];

var groupedData = _.groupBy(data, 'zone');
var result = _.map(groupedData, (value, key) => {
  return {
    "zone": key,
    "groups": value
  }
});

It can be chained, if you like that way:

var result = _.chain(data)
  .groupBy('zone')
  .map((value, key) => {
    return {
      "zone": key,
      "groups": value
    }
  }).value();

_.groupBy transforms your data array into object like this:

{
   "Bottom":[
      /* All entities where zone is "Bottom" */
   ],
   "Neutral axis":[
      /* All entities where zone is "Neutral axis" */
   ]
}

Then we transform this object into array of your desired objects using _.map.

Resources:

https://lodash.com/docs/4.17.15#groupBy

https://lodash.com/docs/4.17.15#map

https://lodash.com/docs/4.17.15#chain