JS filter array if includes string in array

Question

I would like to filter out each in an array if the value of category is of a user selected value.

For example, I have an array of exampleData

[
    {
      "node": {
        "id": "377856cd-9477-58a4-9596-888ebc8c03d5",
        "title": "Tubing & Sledding",
        "category": [
          "Winter"
        ]
      }
    },
    {
      "node": {
        "id": "a7370249-af7a-538a-aaae-91f308575bb8",
        "title": "Snowmobiling",
        "category": [
          "Summer",
          "Winter"
        ]
      }
    },
    {
      "node": {
        "id": "4136389a-77b7-5e07-8c95-1c856983d27b",
        "title": "Snowshoeing",
        "category": [
          "Winter"
        ]
      }
    },
    {
      "node": {
        "id": "79fc5efa-e1a4-5e65-94cd-97a5245ed0af",
        "title": "X-Country Skiing",
        "category": [
          "Winter"
        ]
      }
    }
  ]

And I would like to filter the array to only return the objects with Summer included in the category field array .

To do this, I have tried

const exampleCategory = exampleData.filter(({ node: category }) => {
  activity.category.includes('Summer');
});

Yet, console.log(exampleCategory) shows with zero results.

What have I done wrong here?

Ele · Accepted Answer · 2019-05-02 03:25:41Z

1

You should return the boolean result of calling .includes:

const exampleCategory = exampleData.filter(({ node: { category }}) => {
   return category.includes('Summer');
});

Also, you can directly do that without return

const exampleCategory = exampleData.filter(({ node: { category }}) => category.includes('Summer'));

Example

const exampleData = [{    "node": {      "id": "377856cd-9477-58a4-9596-888ebc8c03d5",      "title": "Tubing & Sledding",      "category": [        "Winter"      ]    }  },  {    "node": {      "id": "a7370249-af7a-538a-aaae-91f308575bb8",      "title": "Snowmobiling",      "category": [        "Summer",        "Winter"      ]    }  },  {    "node": {      "id": "4136389a-77b7-5e07-8c95-1c856983d27b",      "title": "Snowshoeing",      "category": [        "Winter"      ]    }  },  {    "node": {      "id": "79fc5efa-e1a4-5e65-94cd-97a5245ed0af",      "title": "X-Country Skiing",      "category": [        "Winter"      ]    }  }];
const exampleCategory = exampleData.filter(({ node: { category }}) => category.includes('Summer'));

console.log(exampleCategory);

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

edited May 2, 2019 at 3:25

answered May 2, 2019 at 3:21

Ele

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1 Comment

Darren Over a year ago

I feel stupid. Cannot believe that I missed that. Will accept as correct answer as it allows. Cheers

Maheer Ali · Accepted Answer · 2019-05-02 03:29:47Z

You are making two mistakes

You are returning undefined from callback passed to filter. You need to explicitly return the result of includes or use Arrow Function to implicitly return the result.
You are using includes() on wrong value.activity will be undefined. Simply check for element.node.category.includes

const exampleData = [ { "node": { "id": "377856cd-9477-58a4-9596-888ebc8c03d5", "title": "Tubing & Sledding", "category": [ "Winter" ] } }, { "node": { "id": "a7370249-af7a-538a-aaae-91f308575bb8", "title": "Snowmobiling", "category": [ "Summer", "Winter" ] } }, { "node": { "id": "4136389a-77b7-5e07-8c95-1c856983d27b", "title": "Snowshoeing", "category": [ "Winter" ] } }, { "node": { "id": "79fc5efa-e1a4-5e65-94cd-97a5245ed0af", "title": "X-Country Skiing", "category": [ "Winter" ] } } ]

const exampleCategory = exampleData.filter(x => x.node.category.includes('Summer'))

console.log(exampleCategory)

You can also use Object Destructuring.

const exampleData = [ { "node": { "id": "377856cd-9477-58a4-9596-888ebc8c03d5", "title": "Tubing & Sledding", "category": [ "Winter" ] } }, { "node": { "id": "a7370249-af7a-538a-aaae-91f308575bb8", "title": "Snowmobiling", "category": [ "Summer", "Winter" ] } }, { "node": { "id": "4136389a-77b7-5e07-8c95-1c856983d27b", "title": "Snowshoeing", "category": [ "Winter" ] } }, { "node": { "id": "79fc5efa-e1a4-5e65-94cd-97a5245ed0af", "title": "X-Country Skiing", "category": [ "Winter" ] } } ]

const exampleCategory = exampleData.filter(({node:{category}}) => category.includes('Summer'))

console.log(exampleCategory)

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