JavaScript reduce array of objects based on value

Question

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.

The operation you are looking for is called "grouping" by machineId and can be achieved with Array.reduce. Examples of doing that can be found here stackoverflow.com/questions/14446511/… — nbokmans
– nbokmans, Commented May 17, 2022 at 12:43
Does this answer your question? How can I group an array of objects by key? — evolutionxbox
– evolutionxbox, Commented May 17, 2022 at 12:44

R4ncid · Accepted Answer · 2022-05-17 12:48:10Z

2

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'))

answered May 17, 2022 at 12:48

R4ncid

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Comments

Nina Scholz · Accepted Answer · 2022-05-17 12:46:57Z

2

You could take a functiion with data and key and map later the entries.

const
    groupBy = (data, key) => Object
        .entries(data.reduce((r, o) => ((r[o[key]] ??= []).push(o), r), {}))
        .map(([k, data]) => ({ [key]: k, data})),
    data = [{ 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" }]
    result = groupBy(data, 'machineId');

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered May 17, 2022 at 12:46

Nina Scholz

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Comments

cmgchess · Accepted Answer · 2022-05-17 12:45:35Z

The initial grouping can be done using reduce. To get the final values array use Object.values on the reduce result

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"    }  ]
  
  let res = Object.values(arr.reduce((acc,curr)=> {
    acc[curr.machineId] = acc[curr.machineId] || {machineId:curr.machineId, data: []}
    acc[curr.machineId].data.push(curr)
    return acc
  },{}))
  
  console.log(res)

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AlexSp3 · Accepted Answer · 2022-05-17 12:48:51Z

Try this solution:

const 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"}];

const output = [], machineIdx = {};
for (const e of arr) {
  // No records for that machineId 
  if (typeof machineIdx[e.machineId] === 'undefined') {
    // Create record for that machineId
    machineIdx[e.machineId] = output.push({
      machineId: e.machineId,
      data: []
    }) - 1;
  }
  // Spread operator to make a copy of the object
  output[machineIdx[e.machineId]].data.push({ ...e });
}

console.log(output);

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