Javascript - Iterating over a nested array of objects to create a new object

martyno
September 29, 2024
170 views
3 votes
3 Answers

I have a nested array of objects that looks something like this:

[
 [
  {
   name: 'name',
   prettyFormat: 'joe bloggs'
   uselessInfo: 'drjfghsdr'
  },
  {
   name: 'email',
   answer: '[email protected]',
   uselessInfo: 'liodrgjiwe'
  }
 ]
 [
  {
   name: 'name',
   prettyFormat: 'mark obrien',
   uselessInfo: 'drjfghsdr'
  },
  {
   name: 'email',
   answer: 'mark [email protected]',
   uselessInfo: 'liodrgjiwe'
  }
 ]
]

I need to transform this array into something more sensible, actually a JSON object, with the following format:

{
  "LIST": [
    {
      "name": "joe bloggs",
      "email": "[email protected]",
    },
    {
      "name": "mark o'brien",
      "email": "mark [email protected]",

    },
  ]
}

This is my solution:

  let outputBuilder = []

  staffSubmissionsArray.forEach(subArray => {
    let personObj = {}
    subArray.forEach(obj => {
      if (obj.name == 'name') {
        personObj['name'] = obj.prettyFormat
      } if (obj.name == 'email') {
        personObj['email'] = obj.answer
      } 
      outputBuilder.push(personObj)
    })
  })

  console.log(JSON.stringify({ "LIST" : outputBuilder })

This gets everything into the right format, however, each person is getting duplicated, presumably each time I iterate over each object, but I don’t know how to fix this. Do I need to approach this in a different way?

Tags: javascript

Answers

Perhaps you can try using map and reduce:

const data = [
  [
    {
      name: 'name',
      prettyFormat: 'joe bloggs',
      uselessInfo: 'drjfghsdr'
    },
    {
      name: 'email',
      answer: '[email protected]',
      uselessInfo: 'liodrgjiwe'
    }
  ],
  [
    {
      name: 'name',
      prettyFormat: 'mark obrien',
      uselessInfo: 'drjfghsdr'
    },
    {
      name: 'email',
      answer: 'mark [email protected]',
      uselessInfo: 'liodrgjiwe'
    }
  ]
];
const transformedData = {
  LIST: data.map(innerArray => 
    innerArray.reduce((acc, item) => {
      if (item.name === 'name') {
        acc.name = item.prettyFormat;
      } else if (item.name === 'email') {
        acc.email = item.answer;
      }
      return acc;
    }, {})
  )
};
console.log(JSON.stringify(transformedData, null, 2));

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

You can also use only the map method map(), together with the optional chaining .? and the nullish coalescing ?? operators:

const data = [
  [
    {
      name: 'name',
      prettyFormat: 'joe bloggs',
      uselessInfo: 'drjfghsdr'
    },
    {
      name: 'email',
      answer: '[email protected]',
      uselessInfo: 'liodrgjiwe'
    }
  ],
  [
    {
      name: 'name',
      prettyFormat: 'mark obrien',
      uselessInfo: 'drjfghsdr'
    },
    {
      name: 'email',
      answer: 'mark [email protected]',
      uselessInfo: 'liodrgjiwe'
    }
  ]
];

const transformedData = {"LIST": data.map(([obj1, obj2]) => ({
  name: obj1?.prettyFormat ?? obj2?.prettyFormat ?? "Name not found!",
  email: obj1?.answer ?? obj2?.answer ?? "Email not found!"
}))};

console.log(JSON.stringify(transformedData, null, 2));

Another alternative is;

      const staffSubmissionsArray = [
        [
          {
            name: 'name',
            prettyFormat: 'joe bloggs',
            uselessInfo: 'drjfghsdr'
          },
          {
            name: 'email',
            answer: '[email protected]',
            uselessInfo: 'liodrgjiwe'
          }
        ],
        [
          {
            name: 'name',
            prettyFormat: 'mark obrien',
            uselessInfo: 'drjfghsdr'
          },
          {
            name: 'email',
            answer: 'mark [email protected]',
            uselessInfo: 'liodrgjiwe'
          }
        ]
      ];

      let outputBuilder = [];

      for (var i=0; i<staffSubmissionsArray.length; i++){
          outputBuilder.push(
            {
              "name":  staffSubmissionsArray[i][0].prettyFormat, 
              "email": staffSubmissionsArray[i][1].answer
            }
         )
       }

      console.log(JSON.stringify({ "LIST" : outputBuilder }))

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Javascript – Iterating over a nested array of objects to create a new object

Answers