CODEWITHSUNDEEP
node.jstypescripttslint
Digvijay Rathore
Digvijay Rathore

Reputation: 715

Object is possibly 'null'.ts(2531)

I am using Node with Typescript. I am finding a mongodb document and updating some values into it and then saving it. On the statement save it is showing this error. Below is the code:

let user = await User.findById(id);
if (user) {
  user = Object.assign(user, req.body);
  await user.save();  // on this line error is shown
} else {
  throw "User not found";
}

On the line await user.save() it is showing this error.

Upvotes: 1

Views: 2092

Answers (2)

cdimitroulas
cdimitroulas

Reputation: 2539

I'm not sure why, but mutating the user variable seems to be causing the issue.

Rewriting it with a new variable works fine in the typescript playground for me (I had to cheat a bit to avoid having a real Mongoose model and I made up the types, but it should be the same idea):

type User = {
    email: string;
    save: () => Promise<void>
}

declare let user: User | null;

if (user) {
  const newUser = Object.assign(user, { email: "[email protected]"})
  newUser.save();  // on this line error is shown
} else {
  throw "User not found";
}

https://www.typescriptlang.org/play?ssl=1&ssc=1&pln=13&pc=2#code/C4TwDgpgBAqgzhATlAvFA3gKCjqEC2AhgJYA2AXFHMIsQHYDmA3NrnIQG4SUAUAlKgB8UAAqIA9vmIIAPB3HEAJoMwBfTJkUQAxqUKJopCMCgBXBIkrwkUAD5Q6p0qRaZiAMyg9zSAVhza4nTUDhAA7tbIaADyAEYAVjrAAHSEcHDEDHTeFgA0GHhEZJQARMAQ1AACEAAehPhgRsmB+CWqfKx04ZHJ7Fz8TDgA9ENQQVDAABbSUKT00EgSyDNwk+JhdGp4pAgYrFMSYVAlkQ7iJu7ipnSKJSyqQA

Upvotes: 1

captain-yossarian from Ukraine
captain-yossarian from Ukraine

Reputation: 33041

This means that user can be null.

You can use conditional statement:

if(user){
 await user.save()
}

Or optional chaining:

await user?.save()

Upvotes: 1

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