检查阵列存在和状况的最快/最短方法

Question

I feel this is a really simple question but as a beginner I cannot find the answer.

Ultimately I want to check an element exists in an array ( eg userProfile.friendRequests ).

I end up using includes as a simple check ie

checkRequest(friendReqUid) {
  return userProfile.friendRequests.includes(friendReqUid)
}

However sometimes that array might not even exist and the only way that I can see to check the condition is to add a check for the entire array beforehand ie

 checkRequest(friendReq) {
   return userProfile.friendRequest && userProfile.friendRequest.includes(friendReq)
 }

If I do this within the template (to show a button, etc.) this ends up being really long winded way to do this.

Is there a quicker function/way to check that an array exists and if an element is present or not, instead of adding another check for the presence of the actual array?

Thanks

Answer 1

The shortest way to do it that I know of is to default to an empty array if the property is falsy:

(userProfile.friendRequests || []).includes(friendReqUid)

But I usually check if the object exists before accessing the array, so it is more robust:

(userProfile && userProfile.friendRequests || []).includes(friendReqUid)

EDIT : If you want to do the same for push() , you can do this:

userProfile && (userProfile.friendRequests = userProfile.friendRequests || []).push(friendReqUid)

This will initialize the array to [] if it is falsy.

However, you might consider splitting this on separate lines so it is more readable.