Filter out objects from nested objects and arrays

Question

I need to filter this array so it is only left with the correct category codes

const yearLayers= 
     [
        {
            "year": 2016,
            "eventNodes": [
               {"header": "Pearls of Wisdom", "categoryCode": 3,}
             ]
        },
        {
            "year": 2017,
            "eventNodes":[
              {"header": "VENuS Satellite", "categoryCode": 2},
              {"header": "Hope for millions", "categoryCode": 1}
            ]
        },
        {
            "year": 2012,
            "eventNodes": [
              {"header": "green electricity Pioneer", "categoryCode": 1}
              {"header": "This is a header", "categoryCode": 3,}
              {"header": "more titles here", "categoryCode": 1,}
            ]
        }
    ]

This is a snippet of what the array looks like. I need to filter out the objects with the category code that does not === 1. So I left with an array with only categoryCode: 1.

const yearLayers= 
     [
        {
            "year": 2016,
            "eventNodes": []
        },
        {
            "year": 2017,
            "eventNodes":[
              {"header": "Hope for millions", "categoryCode": 1}
            ]
        },
        {
            "year": 2012,
            "eventNodes": [
              {"header": "green electricity Pioneer", "categoryCode": 1}
              {"header": "more titles here", "categoryCode": 1,}
            ]
        }
    ]

I have tried to use array methods, but I cannot seem to reach inside the nested array and the nested objects. I think I am missing something

const filteredArr = yearLayers
            .map(layer => layer.eventNodes)
            .map(node => node.categoryCode)
            .filter(node => node.categoryCode !== 1)

Robby Cornelissen · Accepted Answer · 2021-05-11 08:22:25Z

3

You can use map() in combination with filter() like this:

const formattedWorkbook = [{
    "year": 2016,
    "value": [
       {"header": "Pearls of Wisdom", "categoryCode": 3}
     ]
}, {
    "year": 2017,
    "value":[
      {"header": "VENuS Satellite", "categoryCode": 2},
      {"header": "Hope for millions", "categoryCode": 1}
    ]
}, {
    "year": 2012,
    "value": [
      {"header": "green electricity Pioneer", "categoryCode": 1},
      {"header": "This is a header", "categoryCode": 3},
      {"header": "more titles here", "categoryCode": 1}
    ]
}];

const filter = (data, category) => data.map(({year, value}) => ({
  year,
  eventNodes: value.filter(v => v.categoryCode == category)
}));

console.log(filter(formattedWorkbook, 1));

This avoids modifying the original data.

answered May 11, 2021 at 8:22

Robby Cornelissen

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Comments

DecPK · Accepted Answer · 2021-05-11 08:40:17Z

1

You can easily get the result if you use map in the combination with a filter.

const formattedWorkbook = [
  {
    year: 2016,
    value: [{ header: "Pearls of Wisdom", categoryCode: 3 }],
  },
  {
    year: 2017,
    value: [
      { header: "VENuS Satellite", categoryCode: 2 },
      { header: "Hope for millions", categoryCode: 1 },
    ],
  },
  {
    year: 2012,
    value: [
      { header: "green electricity Pioneer", categoryCode: 1 },
      { header: "This is a header", categoryCode: 3 },
      { header: "more titles here", categoryCode: 1 },
    ],
  },
];

const result = formattedWorkbook.map(({ year, value }) => {
  const filteredValue = value.filter((o) => o.categoryCode === 1);
  return { year, value: filteredValue };
});

console.log(result);

2)

const formattedWorkbook = [
  {
    year: 2016,
    value: [{ header: "Pearls of Wisdom", categoryCode: 3 }],
  },
  {
    year: 2017,
    value: [
      { header: "VENuS Satellite", categoryCode: 2 },
      { header: "Hope for millions", categoryCode: 1 },
    ],
  },
  {
    year: 2012,
    value: [
      { header: "green electricity Pioneer", categoryCode: 1 },
      { header: "This is a header", categoryCode: 3 },
      { header: "more titles here", categoryCode: 1 },
    ],
  },
];

const result = formattedWorkbook.map(({ year, value }) => ({
  year,
  value: value.filter((o) => o.categoryCode === 1),
}));

console.log(result);

edited May 11, 2021 at 8:40

answered May 11, 2021 at 8:20

DecPK

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2 Comments

Jamiec Over a year ago

You've mutated the original objects, which is not necessarily a good idea - it might not make a difference but can often lead to unintended side effects

Jamiec Over a year ago

Just FYI - answers which are code only with no explanation as to what has been done or what has been changed are less useful for future visitors

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