Validation

Before we get into the specifics of validation syntax, please keep the following rules in mind:

Validation is defined in the SchemaType
Validation is middleware. Mongoose registers validation as a pre('save') hook on every schema by default.
You can manually run validation using doc.validate(callback) or doc.validateSync()
Validators are not run on undefined values. The only exception is the required validator.
Validation is asynchronously recursive; when you call Model#save, sub-document validation is executed as well. If an error occurs, your Model#save callback receives it
Validation is customizable

var schema = new Schema({
  name: {
    type: String,
    required: true
  }
});
var Cat = db.model('Cat', schema);

// This cat has no name :(
var cat = new Cat();
cat.save(function(error) {
  assert.equal(error.errors['name'].message,
    'Path `name` is required.');

  error = cat.validateSync();
  assert.equal(error.errors['name'].message,
    'Path `name` is required.');
});

Built-in Validators

Mongoose has several built-in validators.

All SchemaTypes have the built-in required validator. The required validator uses the SchemaType's checkRequired() function to determine if the value satisfies the required validator.
Numbers have min and max validators.
Strings have enum, match, minlength, and maxlength validators.

Each of the validator links above provide more information about how to enable them and customize their error messages.

var breakfastSchema = new Schema({
  eggs: {
    type: Number,
    min: [6, 'Too few eggs'],
    max: 12
  },
  bacon: {
    type: Number,
    required: [true, 'Why no bacon?']
  },
  drink: {
    type: String,
    enum: ['Coffee', 'Tea'],
    required: function() {
      return this.bacon > 3;
    }
  }
});
var Breakfast = db.model('Breakfast', breakfastSchema);

var badBreakfast = new Breakfast({
  eggs: 2,
  bacon: 0,
  drink: 'Milk'
});
var error = badBreakfast.validateSync();
assert.equal(error.errors['eggs'].message,
  'Too few eggs');
assert.ok(!error.errors['bacon']);
assert.equal(error.errors['drink'].message,
  '`Milk` is not a valid enum value for path `drink`.');

badBreakfast.bacon = 5;
badBreakfast.drink = null;

error = badBreakfast.validateSync();
assert.equal(error.errors['drink'].message, 'Path `drink` is required.');

badBreakfast.bacon = null;
error = badBreakfast.validateSync();
assert.equal(error.errors['bacon'].message, 'Why no bacon?');

The `unique` Option is Not a Validator

A common gotcha for beginners is that the unique option for schemas is not a validator. It's a convenient helper for building MongoDB unique indexes. See the FAQ for more information.

var uniqueUsernameSchema = new Schema({
  username: {
    type: String,
    unique: true
  }
});
var U1 = db.model('U1', uniqueUsernameSchema);
var U2 = db.model('U2', uniqueUsernameSchema);

var dup = [{ username: 'Val' }, { username: 'Val' }];
U1.create(dup, function(error) {
  // Race condition! This may save successfully, depending on whether
  // MongoDB built the index before writing the 2 docs.
});

// Need to wait for the index to finish building before saving,
// otherwise unique constraints may be violated.
U2.once('index', function(error) {
  assert.ifError(error);
  U2.create(dup, function(error) {
    // Will error, but will *not* be a mongoose validation error, it will be
    // a duplicate key error.
    assert.ok(error);
    assert.ok(!error.errors);
    assert.ok(error.message.indexOf('duplicate key error') !== -1);
  });
});

// There's also a promise-based equivalent to the event emitter API.
// The `init()` function is idempotent and returns a promise that
// will resolve once indexes are done building;
U2.init().then(function() {
  U2.create(dup, function(error) {
    // Will error, but will *not* be a mongoose validation error, it will be
    // a duplicate key error.
    assert.ok(error);
    assert.ok(!error.errors);
    assert.ok(error.message.indexOf('duplicate key error') !== -1);
  });
});

Custom Validators

If the built-in validators aren't enough, you can define custom validators to suit your needs.

Custom validation is declared by passing a validation function. You can find detailed instructions on how to do this in the SchemaType#validate() API docs.

var userSchema = new Schema({
  phone: {
    type: String,
    validate: {
      validator: function(v) {
        return /\d{3}-\d{3}-\d{4}/.test(v);
      },
      message: props => `${props.value} is not a valid phone number!`
    },
    required: [true, 'User phone number required']
  }
});

var User = db.model('user', userSchema);
var user = new User();
var error;

user.phone = '555.0123';
error = user.validateSync();
assert.equal(error.errors['phone'].message,
  '555.0123 is not a valid phone number!');

user.phone = '';
error = user.validateSync();
assert.equal(error.errors['phone'].message,
  'User phone number required');

user.phone = '201-555-0123';
// Validation succeeds! Phone number is defined
// and fits `DDD-DDD-DDDD`
error = user.validateSync();
assert.equal(error, null);

Async Custom Validators

Custom validators can also be asynchronous. If your validator function returns a promise (like an async function), mongoose will wait for that promise to settle. If the returned promise rejects, or fulfills with the value false, Mongoose will consider that a validation error.

const userSchema = new Schema({
  name: {
    type: String,
    // You can also make a validator async by returning a promise.
    validate: () => Promise.reject(new Error('Oops!'))
  },
  email: {
    type: String,
    // There are two ways for an promise-based async validator to fail:
    // 1) If the promise rejects, Mongoose assumes the validator failed with the given error.
    // 2) If the promise resolves to `false`, Mongoose assumes the validator failed and creates an error with the given `message`.
    validate: {
      validator: () => Promise.resolve(false),
      message: 'Email validation failed'
    }
  }
});

const User = db.model('User', userSchema);
const user = new User();

user.email = '[email protected]';
user.name = 'test';
user.validate().catch(error => {
  assert.ok(error);
  assert.equal(error.errors['name'].message, 'Oops!');
  assert.equal(error.errors['email'].message, 'Email validation failed');
});

Validation Errors

Errors returned after failed validation contain an errors object whose values are ValidatorError objects. Each ValidatorError has kind, path, value, and message properties. A ValidatorError also may have a reason property. If an error was thrown in the validator, this property will contain the error that was thrown.

var toySchema = new Schema({
  color: String,
  name: String
});

var validator = function(value) {
  return /red|white|gold/i.test(value);
};
toySchema.path('color').validate(validator,
  'Color `{VALUE}` not valid', 'Invalid color');
toySchema.path('name').validate(function(v) {
  if (v !== 'Turbo Man') {
    throw new Error('Need to get a Turbo Man for Christmas');
  }
  return true;
}, 'Name `{VALUE}` is not valid');

var Toy = db.model('Toy', toySchema);

var toy = new Toy({ color: 'Green', name: 'Power Ranger' });

toy.save(function (err) {
  // `err` is a ValidationError object
  // `err.errors.color` is a ValidatorError object
  assert.equal(err.errors.color.message, 'Color `Green` not valid');
  assert.equal(err.errors.color.kind, 'Invalid color');
  assert.equal(err.errors.color.path, 'color');
  assert.equal(err.errors.color.value, 'Green');

  // This is new in mongoose 5. If your validator throws an exception,
  // mongoose will use that message. If your validator returns `false`,
  // mongoose will use the 'Name `Power Ranger` is not valid' message.
  assert.equal(err.errors.name.message,
    'Need to get a Turbo Man for Christmas');
  assert.equal(err.errors.name.value, 'Power Ranger');
  // If your validator threw an error, the `reason` property will contain
  // the original error thrown, including the original stack trace.
  assert.equal(err.errors.name.reason.message,
    'Need to get a Turbo Man for Christmas');

  assert.equal(err.name, 'ValidationError');
});

Cast Errors

Before running validators, Mongoose attempts to coerce values to the correct type. This process is called casting the document. If casting fails for a given path, the error.errors object will contain a CastError object.

Casting runs before validation, and validation does not run if casting fails. That means your custom validators may assume v is null, undefined, or an instance of the type specified in your schema.

const vehicleSchema = new mongoose.Schema({
  numWheels: { type: Number, max: 18 }
});
const Vehicle = db.model('Vehicle', vehicleSchema);

const doc = new Vehicle({ numWheels: 'not a number' });
const err = doc.validateSync();

err.errors['numWheels'].name; // 'CastError'
// 'Cast to Number failed for value "not a number" at path "numWheels"'
err.errors['numWheels'].message;

Required Validators On Nested Objects

Defining validators on nested objects in mongoose is tricky, because nested objects are not fully fledged paths.

var personSchema = new Schema({
  name: {
    first: String,
    last: String
  }
});

assert.throws(function() {
  // This throws an error, because 'name' isn't a full fledged path
  personSchema.path('name').required(true);
}, /Cannot.*'required'/);

// To make a nested object required, use a single nested schema
var nameSchema = new Schema({
  first: String,
  last: String
});

personSchema = new Schema({
  name: {
    type: nameSchema,
    required: true
  }
});

var Person = db.model('Person', personSchema);

var person = new Person();
var error = person.validateSync();
assert.ok(error.errors['name']);

Update Validators

In the above examples, you learned about document validation. Mongoose also supports validation for update(), updateOne(), updateMany(), and findOneAndUpdate() operations. Update validators are off by default - you need to specify the runValidators option.

To turn on update validators, set the runValidators option for update(), updateOne(), updateMany(), or findOneAndUpdate(). Be careful: update validators are off by default because they have several caveats.

var toySchema = new Schema({
  color: String,
  name: String
});

var Toy = db.model('Toys', toySchema);

Toy.schema.path('color').validate(function (value) {
  return /red|green|blue/i.test(value);
}, 'Invalid color');

var opts = { runValidators: true };
Toy.updateOne({}, { color: 'not a color' }, opts, function (err) {
  assert.equal(err.errors.color.message,
    'Invalid color');
});

Update Validators and `this`

There are a couple of key differences between update validators and document validators. In the color validation function above, this refers to the document being validated when using document validation. However, when running update validators, the document being updated may not be in the server's memory, so by default the value of this is not defined.

var toySchema = new Schema({
  color: String,
  name: String
});

toySchema.path('color').validate(function(value) {
  // When running in `validate()` or `validateSync()`, the
  // validator can access the document using `this`.
  // Does **not** work with update validators.
  if (this.name.toLowerCase().indexOf('red') !== -1) {
    return value !== 'red';
  }
  return true;
});

var Toy = db.model('ActionFigure', toySchema);

var toy = new Toy({ color: 'red', name: 'Red Power Ranger' });
var error = toy.validateSync();
assert.ok(error.errors['color']);

var update = { color: 'red', name: 'Red Power Ranger' };
var opts = { runValidators: true };

Toy.updateOne({}, update, opts, function(error) {
  // The update validator throws an error:
  // "TypeError: Cannot read property 'toLowerCase' of undefined",
  // because `this` is **not** the document being updated when using
  // update validators
  assert.ok(error);
});

The `context` option

The context option lets you set the value of this in update validators to the underlying query.

toySchema.path('color').validate(function(value) {
  // When running update validators with the `context` option set to
  // 'query', `this` refers to the query object.
  if (this.getUpdate().$set.name.toLowerCase().indexOf('red') !== -1) {
    return value === 'red';
  }
  return true;
});

var Toy = db.model('Figure', toySchema);

var update = { color: 'blue', name: 'Red Power Ranger' };
// Note the context option
var opts = { runValidators: true, context: 'query' };

Toy.updateOne({}, update, opts, function(error) {
  assert.ok(error.errors['color']);
});

Update Validators Only Run On Updated Paths

The other key difference that update validators only run on the paths specified in the update. For instance, in the below example, because 'name' is not specified in the update operation, update validation will succeed.

When using update validators, required validators only fail when you try to explicitly $unset the key.

var kittenSchema = new Schema({
  name: { type: String, required: true },
  age: Number
});

var Kitten = db.model('Kitten', kittenSchema);

var update = { color: 'blue' };
var opts = { runValidators: true };
Kitten.updateOne({}, update, opts, function(err) {
  // Operation succeeds despite the fact that 'name' is not specified
});

var unset = { $unset: { name: 1 } };
Kitten.updateOne({}, unset, opts, function(err) {
  // Operation fails because 'name' is required
  assert.ok(err);
  assert.ok(err.errors['name']);
});

Update Validators Only Run For Some Operations

One final detail worth noting: update validators only run on the following update operators:

$set
$unset
$push (>= 4.8.0)
$addToSet (>= 4.8.0)
$pull (>= 4.12.0)
$pullAll (>= 4.12.0)

For instance, the below update will succeed, regardless of the value of number, because update validators ignore $inc.

Also, $push, $addToSet, $pull, and $pullAll validation does not run any validation on the array itself, only individual elements of the array.

var testSchema = new Schema({
  number: { type: Number, max: 0 },
  arr: [{ message: { type: String, maxlength: 10 } }]
});

// Update validators won't check this, so you can still `$push` 2 elements
// onto the array, so long as they don't have a `message` that's too long.
testSchema.path('arr').validate(function(v) {
  return v.length < 2;
});

var Test = db.model('Test', testSchema);

var update = { $inc: { number: 1 } };
var opts = { runValidators: true };
Test.updateOne({}, update, opts, function(error) {
  // There will never be a validation error here
  update = { $push: [{ message: 'hello' }, { message: 'world' }] };
  Test.updateOne({}, update, opts, function(error) {
    // This will never error either even though the array will have at
    // least 2 elements.
  });
});

On $push and $addToSet

New in 4.8.0: update validators also run on $push and $addToSet

var testSchema = new Schema({
  numbers: [{ type: Number, max: 0 }],
  docs: [{
    name: { type: String, required: true }
  }]
});

var Test = db.model('TestPush', testSchema);

var update = {
  $push: {
    numbers: 1,
    docs: { name: null }
  }
};
var opts = { runValidators: true };
Test.updateOne({}, update, opts, function(error) {
  assert.ok(error.errors['numbers']);
  assert.ok(error.errors['docs']);
});

Validation

Validation

Built-in Validators

The unique Option is Not a Validator

Custom Validators

Async Custom Validators

Validation Errors

Cast Errors

Required Validators On Nested Objects

Update Validators

Update Validators and this

The context option

Update Validators Only Run On Updated Paths

Update Validators Only Run For Some Operations

On $push and $addToSet

The `unique` Option is Not a Validator

Update Validators and `this`

The `context` option