trim() in Mongoose Schemas

Jul 1, 2024

Mongoose has a trim() SchemaType option that registers a setter which automatically trims leading and trailing whitespace from the given string. Whitespace includes spaces, newlines \n, tabs \t, carriage return \r, and others.

const userSchema = new Schema({
  name: {
    type: String,
    trim: true // Registers a setter which calls `trim()` automatically
const UserModel = mongoose.model('User', userSchema);

const user = new User({ name: '  da Vinci  ' });; // 'da Vinci', without leading and trailing spaces

Whenever you set in the above example, Mongoose will automatically call trim() to trim leading and trailing whitespace from the user's name. This ensures that any new name properties you save to your database will have no leading or trailing whitespace.

Mongoose will also trim() the name property in your query filters by default. So if you run a query by name, Mongoose will trim() the name by default.

// The following is equivalent to querying by `{ name: 'da Vinci' }`
// because Mongoose will `trim()` the `name` property.
await UserModel.findOne({ name: '  da Vinci  ' });

Caveat: trim is Setter Only, No Getter

trim() is a setter, so if you have existing documents in your database with leading or trailing whitespace, Mongoose will not trim() that whitespace when loading the document from MongoDB.

const _id = new mongoose.Types.ObjectId();
// Insert a document with leading and trailing whitespace, bypassing Mongoose
await UserModel.collection.insertOne({ _id, name: '  da Vinci  ' });

const doc = await UserModel.findById(_id);; // '  da Vinci  ', with leading and trailing whitespace

To apply the setter, you can set the document's name to itself as follows.

// The following triggers Mongoose's setters, so will apply `trim()`. =;; // 'da Vinci', no leading or trailing whitespace
await; // Persist the document's new `name`

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