Google Firebase Error(Function returned undefined, expected Promise or value)

Question

I\'m developing Server with Firebase.

I had copied Google Developer\'s Video on Youtube.

It works well, but on log there is an error:

Answer 1

Adding to what @bob-snyder said, your problem is that your returning undefined under a condition.

if (post.sanitized) return;

My suggestion is to use a single exit point, which is a common tip when programming. Article.

Example

// code...
const SUCCESS_CODE = 0;

exports.sanitizePost = functions.database
    .ref('/posts/{pushId}')
    .onWrite(event => {
        const post = event.data.val();

        let response = Promise.resolve(SUCCESS_CODE);

        if (!post.sanitized) {
            console.log('Sanitizing new post', event.params.pushId);
            console.log(post);
            post.sanitized = true;
            post.title = sanitize(post.title);
            post.body = sanitize(post.body);
            response = event.data.ref.set(post); 
        }

        return response;
    })