Could I potentially receive a null value in the event that I am provided with an empty array?

In my Typescript code, I am dealing with two arrays of objects. I need to find matches between the items in the first array and the second array. However, when there is no match, it returns an empty array:

Here 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
  }
]

To find the matches, I use the following approach:

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)

})

The above code snippet produces this output:

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

When there is no match, an empty array is returned. Is there a way to have it return nothing instead?

My issue arises when trying to access the 'wheel' property from an empty array, resulting in the error message:

Error: Cannot read properties of undefined (reading 'wheel')

Answer №1

Is it possible to return nothing if no match is found, rather than an empty array?

A simple solution would be to use null instead of the empty array. However, this approach may not resolve the following error:

Error: Cannot read properties of undefined (reading 'wheel')

Using null might just replace one error with another. In order to avoid this issue, consider checking the length of the array before using it. Here's an example:

if (result.length > 0) {
    const wheelRes = result[0].wheel;
    // Implement your logic for wheelRes here...
}

Alternatively, based on the usage of result[0] (assuming only expecting a single element from the filter operation), you can switch to using find instead:

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

If no match is found with find, it will return

undefined</code which you can handle as follows:</p>
<pre><code>if (result) {
    const wheelRes = result.wheel;
    // Implement your logic for wheelRes here...
}

Answer №2

Ensure the array is not empty before trying to access its elements.

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; // Make sure the result array has elements before accessing the first one

  console.log(result)

})

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