JavaScript reduce array of objects based on value

May 17, 2022

I am currently trying to use reduce to merge objects together when objects contain the a specific value attached to the machineId key.

Beneath is the input:

var arr = [
    {
      "id":"4055",
      "severity": "High",
      "public": true,
      "machineId": "48ed3",
      "machineName": "powerb"
    },
    {
      "id":"4045",
      "severity": "High",
      "public": true,
      "machineId": "48ed3",
      "machineName": "powerb"
    },
    {
      "id":"3433",
      "severity": "High",
      "public": true,
      "machineId": "43h5",
      "machineName": "powerva"
    }
  ]

Beneath is the expected output:

  var output = [
    {
        machineId: "48ed3",
        data: [
            {
                "id":"4055",
                "severity": "High",
                "public": true,
                "machineId": "48ed3",
                "machineName": "powerb"
            },
            {
                "id":"4045",
                "severity": "High",
                "public": true,
                "machineId": "48ed3",
                "machineName": "powerb"
            }
        ] 
    },
    {
        machineId: "43h5",
        data: [
            {
                "id":"3433",
                "severity": "High",
                "public": true,
                "machineId": "43h5",
                "machineName": "powerva"
              }
        ]
    }
];

This is what I currently have as my solution:

const result = Array.from(new Set(cveId.map(s => s.machineId)))
.map(lab => {
return {
machineId: lab,
cveId: cveId.filter(s => s.machineId === lab).map(CVE => CVE.cveId)
}
})
  
console.log(result);

I’ve also tried creating an empty array and using !arr.contains() to push items into a new object but I’m struggling to get a working solution.

I’d appreciate any assistance with this.

Thanks.

>Solution :

you can do this

const groupByKey = (data, key) => Object.values(
  data.reduce((res, item) => {
   const value = item[key]
   const existing = res[value] || {[key]: value, data:[]}
   return {
     ...res,
     [value] : {
       ...existing,
       data: [...existing.data, item]
     }
   } 
  }, {})
)

var arr = [
    {
      "id":"4055",
      "severity": "High",
      "public": true,
      "machineId": "48ed3",
      "machineName": "powerb"
    },
    {
      "id":"4045",
      "severity": "High",
      "public": true,
      "machineId": "48ed3",
      "machineName": "powerb"
    },
    {
      "id":"3433",
      "severity": "High",
      "public": true,
      "machineId": "43h5",
      "machineName": "powerva"
    }
  ]
  
  console.log(groupByKey(arr, 'machineId'))