CODEWITHSUNDEEP
javascript
Hommer Smith
Hommer Smith

Reputation: 27852

Arrow function with return assignment not working even with parenthesis

I have the following filter:

const auxHash = {};
myArray.filter(house =>
  house.members === 3 &&
  auxHash[house.id] ? false : auxHash[house.id] = true
)

And I get a lint error saying that an arrow function should not return an assignment. I have tried this too:

const auxHash = {};
myArray.filter(house =>
  house.members === 3 &&
  auxHash[house.id] ? false : (auxHash[house.id] = true)
)

But same problem. How can I solve this?

To clarify. I am trying to filter out elements of an array which attribute members is different than 3, and also I am trying to remove duplicate elements based on the attribute id (that's why I am using the hash).

Upvotes: 1

Views: 2388

Answers (2)

John S
John S

Reputation: 101

You're reformatting the exact same statement and ignoring the linter's error. You are returning an assignment. That is your problem. You're doing it right here - auxHash[house.id] = true

Your ternary resolves to false or auxHash[house.id] = true

So, refactor to return an actual value - 

const auxHash = {};
myArray.filter(house => {
  if(house.members === 3 && auxHash[house.id]) {
      return false;
  } else {
      auxHash[house.id] = true;
      return true;
  }
});

You can write it more concisely but I stretched it out to make it clear.

Upvotes: 0

Suren Srapyan
Suren Srapyan

Reputation: 68665

Before question edit.

If you use {} body you need explicitly return a result from that function.

const auxHash = {};
myArray.filter(house => {
    return house.members === 3 && auxHash[house.id] ? false : auxHash[house.id] = true;
})

Also, if your statement is one line, you can omit the {} part and remove return

const auxHash = {};
myArray.filter(house => house.members === 3 && auxHash[house.id] ? false : auxHash[house.id] = true)

Upvotes: 2

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