How can I solve the error TS2532 Object is possibly undefined

Question

I m trying to rebuild a web app example that uses Firebase Cloud Functions and Firestore  When deploying a function I get the following error    src index ts 45 18 - error TS2532  Object is possibly  undefined   45     const data   change after data      This is the function   export const archiveChat   functions firestore    document  chats  chatId       onUpdate change   gt        const data   change after data         const maxLen   100      const msgLen   data messages length      const charLen   JSON stringify data  length       const batch   db batch         if  charLen  gt   10000    msgLen  gt   maxLen              Always delete at least 1 message       const deleteCount   msgLen - maxLen  lt   0   1   msgLen - maxLen       data messages splice 0  deleteCount          const ref   db collection  chats   doc change after id          batch set ref  data    merge  true            return batch commit          else         return null                I m just trying to deploy the function to test it  And already searched the web for similar problems  but couldn t find any other posts that match my problem

User · Accepted Answer

With the release of TypeScript 3 7  optional chaining  the   operator  is now officially available  As such  you can simplify your expression to the following  const data   change  after  data     You may read more about it from that version s release notes  which cover other interesting features released on that version  Run the following to install the latest stable release of TypeScript  npm install typescript  That being said  Optional Chaining can be used alongside Nullish Coalescing to provide a fallback value when dealing with null or undefined values const data   change  after  data      someOtherData

User · Answer

Edit   Update  If you are using Typescript 3 7 or newer you can now also do      const data   change  after  data         if  data          console error  No data here            return null            const maxLen   100      const msgLen   data messages length      const charLen   JSON stringify data  length       const batch   db batch         if  charLen  gt   10000    msgLen  gt   maxLen              Always delete at least 1 message       const deleteCount   msgLen - maxLen  lt   0   1   msgLen - maxLen       data messages splice 0  deleteCount          const ref   db collection  quot chats quot   doc change after id          batch set ref  data    merge  true            return batch commit          else         return null         Original Response Typescript is saying that change or data is possibly undefined  depending on what onUpdate returns   So you should wrap it in a null undefined check  if change  amp  amp  change after  amp  amp  change after data       const data   change after data         const maxLen   100      const msgLen   data messages length      const charLen   JSON stringify data  length       const batch   db batch         if  charLen  gt   10000    msgLen  gt   maxLen              Always delete at least 1 message       const deleteCount   msgLen - maxLen  lt   0   1   msgLen - maxLen       data messages splice 0  deleteCount          const ref   db collection  quot chats quot   doc change after id          batch set ref  data    merge  true            return batch commit          else         return null           If you are 100  sure that your object is always defined then you can put this  const data   change after  data

User · Answer

For others facing a similar problem to mine  where you know a particular object property cannot be null  you can use the non-null assertion operator     after the item in question  This was my code    const naciStatus   dataToSend naci  statusNACI    if  typeof naciStatus     quot undefined quot         switch  naciStatus          case  quot AP quot           dataToSend naci certificateStatus    quot FALSE quot           break        case  quot AS quot         case  quot WR quot           dataToSend naci certificateStatus    quot TRUE quot           break        default          dataToSend naci certificateStatus    quot  quot              And because dataToSend naci cannot be undefined in the switch statement  the code can be updated to include exclamation marks as follows    const naciStatus   dataToSend naci  statusNACI    if  typeof naciStatus     quot undefined quot         switch  naciStatus          case  quot AP quot           dataToSend naci  certificateStatus    quot FALSE quot           break        case  quot AS quot         case  quot WR quot           dataToSend naci  certificateStatus    quot TRUE quot           break        default          dataToSend naci  certificateStatus    quot  quot

[typescript] How can I solve the error 'TS2532: Object is possibly 'undefined'?

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