Question 49566 in Javascript Question posted in
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Is it possible to return null if I get an empty array? – Javascript

I have two arrays of objects in Typescript, I am going through the first array to get the matches of the second array, my problem is that if it doesn’t match it returns an empty array:

This is the first array:

let info = [
  {
    "brand": "bmw",
    "year": "2020",
    "country": "spain"
  },
  {
    "brand": "ford",
    "year": "2015",
    "country": "italy"
  },
  {
    "brand": "audi",
    "year": "2010",
    "country": "colombia"
  }
]

This is the second array:

let dataInit = [
  {
    "brand": "bmw",
    "year": "2020",
    "wheel": 18
  },
  {
    "brand": "audi",
    "year": "2010",
    "wheel": 17
  }
]

This is what I do to get the matches:

info.forEach((itemInfo: any) => {

  const { brand, year } = itemInfo

  const result = dataInit.filter((itemInit: any) =>
    brand.toUpperCase() === itemInit.brand.toUpperCase() && year.toUpperCase() === itemInit.year.toUpperCase()
  )

  const wheelRes = result[0].wheel;

  console.log(result)

})

This is what it returns:

1. [{"brand": "bmw","year": "2020","wheel": 18}]
2. []
3. [{"brand": "audi","year": "2010","wheel": 17}]

Finding no match returns [], is it possible to return nothing?

This is my problem:

I want to get the value of the ‘wheel’ property, but when an empty array comes I get an error: Error: Cannot read properties of undefined (reading 'wheel')

Tags:

2

Answers


  1. 0

    You can just check if the array is empty before accessing it.

    info.forEach((itemInfo: any) => {

  const { brand, year } = itemInfo

  const result = dataInit.filter((itemInit: any) =>
    brand.toUpperCase() === itemInit.brand.toUpperCase() && year.toUpperCase() === itemInit.year.toUpperCase()
  )

  const wheelRes = result.length > 0 ? result[0].wheel : null; // Check if result array is not empty before accessing its first element

  console.log(result)

})
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  2. 0

    Finding no match returns [], is it possible to return nothing?

    Of course, just use null instead of the empty array. However, that won’t solve this problem:

    Error: Cannot read properties of undefined (reading ‘wheel’)

    It would just replace that error with a new error, and for the same reason.

    Instead, check the length of the array before trying to use it. For example:

    if (result.length > 0) {
    const wheelRes = result[0].wheel;
    // then whatever you plan to do with wheelRes...
}

    Alternatively… from the use of result[0] (hard-coded first array element) it seems like you only ever expect one element to be found by the filter operation. If that’s the case then you can use find instead:

    const result = dataInit.find((itemInit: any) =>
  brand.toUpperCase() === itemInit.brand.toUpperCase() && year.toUpperCase() === itemInit.year.toUpperCase()
)

    If no match is found then find will return undefined, which you can check the same way:

    if (result) {
    const wheelRes = result.wheel;
    // then whatever you plan to do with wheelRes...
}
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