Chai - Assert that all elements in the array are equal to a given value with

Question

I have this array of strings:

[ "apple", "apple", "apple", "apple", "apple", "apple", ]

Is it possible to make an assertion with Chai that all elements in the array are equal to the certain value?

arrayFromApiResponse = [ "apple", "apple", "apple", "apple", "apple", "apple", ]
expectedFruit = "apple"

expect(arrayFromApiResponse).to ???

I need to test that each value in the arrayFromApiResponse is "apple"

I found this https://github.com/chaijs/Chai-Things

Seems like with this library it can be accomplished like this:

expect(arrayFromApiResponse).should.all.be.a(expectedFruit)

But is it possible to achieve this without additional library? Maybe I can make some changes to arrayFromApiResponse so it can be validated by Chai?

UPD: I have updated the question title to prevent marking my question as duplicate with reference to this type of questions: Check if all values of array are equal

Does this answer your question? Check if all values of array are equal — Ilijanovic
– Ilijanovic, Commented Jun 2, 2020 at 9:16

Daan · Accepted Answer · 2020-06-02 09:08:34Z

1

You could use the every() method.

const arrayFromApiResponse = [ "apple", "apple", "apple", "apple", "apple", "apple", ]
const expectedFruit = "apple"

const allAreExpectedFruit = arrayFromApiResponse.every(x => x === expectedFruit);

console.log(allAreExpectedFruit);

edited Jun 2, 2020 at 9:08

answered Jun 2, 2020 at 9:03

Daan

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zfj3ub94rf576hc4eegm · Accepted Answer · 2020-06-02 09:21:39Z

1

const arrayFromApiResponse = [ "apple", "apple", "apple", "apple", "apple", "apple"]
const expectedFruit = "apple"

You can do this with filter() but the most efficient would be a good old for loop:

function test(arr, val){
  for(let i=0; i<arrayFromApiResponse.length; i++){
    if(arr[i] !== val) {
      return false;
    }
  }

  return true;
}

The reason this is more efficient is that this function will terminate as soon as it sees a value which doesn't equal the expected value. Other functions will traverse the entire array, which can be extremely inefficient. Use it like this:

expect(test(arrayFromApiResponse, expectedFruit)).toBe(true);

answered Jun 2, 2020 at 9:21

zfj3ub94rf576hc4eegm

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1 Comment

Daan Over a year ago

every() works exactly the same, it returns false as soon as it has found an element that returns false. This can be found under "Description".

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