add mongoose trim tutorial

vkarpov15 · vkarpov15 · commit 884aeac69641 · 2024-07-01T16:19:08.000-04:00
diff --git a/src/tutorials.js b/src/tutorials.js
@@ -5,6 +5,14 @@ const moment = require('moment');
 const axiosPath = require('./axiosPath');
 
 const tutorials = [
+  {
+    title: 'trim() in Mongoose Schemas',
+    raw: './tutorials/mongoose/trim.md',
+    url: '/tutorials/mongoose/trim',
+    description: 'The `trim()` option in Mongoose schema definitions makes Mongoose automatically call `String.prototype.trim()` on string fields. Here\'s how it works.',
+    tags: ['mongoose'],
+    date: moment('2024-07-01')
+  },
   {
     title: 'Set Whether a Checkbox is Checked in Vue',
     raw: './tutorials/vue/checkbox-checked.md',
diff --git a/tutorials/mongoose/trim.md b/tutorials/mongoose/trim.md
@@ -0,0 +1,50 @@
+Mongoose has a `trim()` [SchemaType option](https://mongoosejs.com/docs/schematypes.html#schematype-options) that registers a [setter](https://mongoosejs.com/docs/tutorials/getters-setters.html) which automatically [trims](/tutorials/fundamentals/trim-string) leading and trailing whitespace from the given string.
+[Whitespace](https://developer.mozilla.org/en-US/docs/Glossary/Whitespace) includes spaces, newlines `\n`, tabs `\t`, carriage return `\r`, and others.
+
+```javascript
+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  ' });
+user.name; // 'da Vinci', without leading and trailing spaces
+```
+
+Whenever you set `user.name` 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.
+
+```javascript
+// 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.
+
+```javascript
+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);
+doc.name; // '  da Vinci  ', with leading and trailing whitespace
+```
+
+To apply the setter, you can set the document's `name` to itself as follows.
+
+```javascript
+// The following triggers Mongoose's setters, so will apply `trim()`.
+doc.name = doc.name;
+
+doc.name; // 'da Vinci', no leading or trailing whitespace
+await doc.save(); // Persist the document's new `name`
+```
