Mongoose middleware (pre/post hooks) in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a pre-save hook that logs a message before saving a document.

Express

schema.pre('save', function(next) {
  console.log('About to save document');
  [1]();
});

Drag options to blanks, or click blank then click option'

Acallback

Bdone

Cnext

Dproceed

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to call the next function, causing the save to hang.

Calling a wrong function name like done or callback.

The next function must be called to continue the middleware chain in Mongoose pre hooks.

2fill in blank

medium

Complete the code to add a post-save hook that logs the saved document.

Express

schema.post('save', function(doc) {
  console.log('Document saved:', [1]);
});

Drag options to blanks, or click blank then click option'

Adoc

Bthis

Cdocument

DsavedDoc

Attempts:

3 left

💡 Hint

Common Mistakes

Using this instead of the passed document in post hooks.

Trying to access document properties without the argument.

In post-save hooks, the saved document is passed as the first argument, commonly named doc.

3fill in blank

hard

Fix the error in the pre-remove hook to properly call the next middleware.

Express

schema.pre('remove', function([1]) {
  console.log('Removing document');
  next();
});

Drag options to blanks, or click blank then click option'

Adone

Bnext

Ccallback

Dproceed

Attempts:

3 left

💡 Hint

Common Mistakes

Not declaring the next parameter but calling next() inside the function.

Using a different parameter name but calling next().

The middleware function must declare next as a parameter to call it properly.

4fill in blank

hard

Fill both blanks to create a pre-find hook that modifies the query to only find active users.

Express

schema.pre('[1]', function() {
  this.[2]({ active: true });
});

Drag options to blanks, or click blank then click option'

Afind

Bwhere

Cdelete

Dsave

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong hook name like 'save' or 'delete'.

Calling a method that does not exist on the query object.

The pre-find hook runs before a find query. The this context is the query, so calling this.where() modifies the query conditions.

5fill in blank

hard

Fill all three blanks to create a post-update hook that logs the update result and calls next.

Express

schema.post('[1]', function(result, [2]) {
  console.log('Update result:', [3]);
  next();
});

Drag options to blanks, or click blank then click option'

AupdateOne

Bnext

Cresult

Dsave

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong hook name like 'save'.

Swapping the order of parameters.

Not calling next() to continue middleware.

The post-update hook listens to 'updateOne'. The second parameter is the next callback. The first parameter is the update result.