Extract data from arrays nested within object properties

Question

I am trying to get some data out of my arrays but I always seem to struggle with arrays. My data takes the following structure

{
    tempAttachments: [{
            _id: "12345-678910",
            bytes: 412051,
            file: 'File',
            size: 411532,
            title: "someFile.csv",
            headers: ['optionOne', undefined, 'optionTwo', undefined, undefined, 'optionThree'],
            type: "file",
            fileType: "typeOne"
        }, {
            _id: "9999-2222",
            bytes: 12345,
            file: 'File',
            size: 23456,
            title: "anotherFile.csv",
            headers: ['optionOne'],
            type: "file",
            fileType: "typeTwo"
        }
    ]
}

I am trying the get the headers part out into its own array. The indexes are important, as they relate to something. I am also using the fileType as an indentifier. So my aim is to end up with something like this

[
  {
    "typeOne": [
      "optionOne",
      "optionTwo",
      "optionThree"
    ]
  },
  {
    "typeTwo": [
      "optionOne"
    ]
  }
]

As you can see I am ignoring the undefined options. So what I am currently trying is this

const mapping = {}
for (const attachment of this.tempAttachments) {
  for (const [index, header] of attachment.headers.entries() || []) {
    mapping[attachment.fileType] = [
      index, header
    ]
  }
}

Unfortunately, the results are as follows

[
  {
    "typeOne": [
      0,
      "optionOne"
    ]
  },
  {
    "typeTwo": [
      0,
      "optionOne"
    ]
  }
]

So how can I achieve the output I am after?

Thanks

Yevhen Horbunkov · Accepted Answer · 2020-06-26 11:14:02Z

2

You may use Array.prototype.map() together with Array.prototype.filter() to get rid of undefind's inside header:

const src = {tempAttachments:[{_id:"12345-678910",bytes:412051,file:'File',size:411532,title:"someFile.csv",headers:['optionOne',undefined,'optionTwo',undefined,undefined,'optionThree'],type:"file",fileType:"typeOne"},{_id:"9999-2222",bytes:12345,file:'File',size:23456,title:"anotherFile.csv",headers:['optionOne'],type:"file",fileType:"typeTwo"}]},

      result = src
        .tempAttachments
        .map(({headers,fileType}) => ({
          [fileType]: headers.filter(Boolean)
        }))

      
console.log(result)

.as-console-wrapper{min-height:100%;}

edited Jun 26, 2020 at 11:14

answered Jun 26, 2020 at 10:19

Yevhen Horbunkov

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3 Comments

katie hudson Over a year ago

How comes you changed your answer? The first one was actually correct, as it also displays the required index.

Yevhen Horbunkov Over a year ago

I have appended filtering out undefined from headers, not it provides your expected output exactly

katie hudson Over a year ago

Your first answer seemed correct. I was not getting any undefined values and it contained the index

Krzysztof Krzeszewski · Accepted Answer · 2020-06-26 10:23:17Z

1

Nothing a simple map and filter couldn't do

const arrays = [
  {headers: ["optionOne", undefined, "optionTwo", undefined, undefined, "optionThree"], fileType:"typeOne"},
  {headers: ["optionOne"], fileType:"typeTwo"},
]

function filter(option){
  return option !== undefined
}

const result = arrays.reduce((result, element) => ({...result, [element.fileType]: element.headers.filter(filter)}), {})

console.log(result)

answered Jun 26, 2020 at 10:23

Krzysztof Krzeszewski

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Comments

Siva Kondapi Venkata · Accepted Answer · 2020-06-26 10:27:21Z

1

Use map and filter

const data = [
  {
    headers: [
      "optionOne",
      undefined,
      "optionTwo",
      undefined,
      undefined,
      "optionThree",
    ],
    fileType: "typeOne",
  },
  { headers: ["optionOne"], fileType: "typeTwo" },
];
const res = data.map(({ headers, fileType }) => ({
  [fileType]: headers.filter(Boolean),
}));

console.log(res);

answered Jun 26, 2020 at 10:27

Siva Kondapi Venkata

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1 Comment

Krzysztof Krzeszewski Over a year ago

this will remove all falsey values, not only undefined

Rishabh Garg · Accepted Answer · 2020-06-26 10:35:11Z

0

You can try

tempAttachments.map(
  ({headers,fileType}) => {
    return ({[fileType]: headers.filter((val) => val)})
  }
)

answered Jun 26, 2020 at 10:35

Rishabh Garg

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Comments

Nithish · Accepted Answer · 2020-06-26 10:57:56Z

0

const data = [{_id:'12345-678910',bytes:412051,file:'File',size:411532,title:'someFile.csv',headers:['optionOne',undefined,'optionTwo',undefined,undefined,'optionThree',],type:'file',fileType:'typeOne',},{_id:'9999-2222',bytes:12345,file:'File',size:23456,title:'anotherFile.csv',headers:['optionOne'],type:'file',fileType:'typeTwo',},];;

const result = data.map(d => {
  let headers = [];
  d.headers.forEach((h, index) => {
    if (!(h === undefined || h === null)) headers.push({ [index]: h });
  });

  return {
    [d.fileType]: [...headers],
  };
});
console.log(result);

.as-console-wrapper{min-height:100%;}

answered Jun 26, 2020 at 10:57

Nithish

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