Remove generated string from Mongoose schema with custom validation

Question

I have a schema with a custom validation.

const schema = new mongoose.Schema({
    username: {
        type: String,
        required: true,
        validate: {
            validator: /^[a-zA-Z0-9_]{3,16}$/, 
            message: "Usernames must be 3 to 16 characters long and contain only alphanumeric characters and underscores (_)."
        },
    },
    // ...other things
});

However, the validation message comes out like this when I type an invalid username:

User validation failed: username: Usernames must be 3 to 16 characters long and contain only alphanumeric characters and underscores (_).

How do I get rid of the part of the string at the start that says User validation failed: username: ?

Answer 1

The format is embedded into the ValidationError class. Short of monkey patching that class, I can't see a way to easily change the format.

One option could be to run validation before being thrown by the model:

const user = new User({ username: 'ab' })
const error = user.validateSync()
console.log(error.errors['username'].message)

Or handle ValidationError when caught:

try {
  const user = new User({ username: 'ab' })
  await user.save()
} catch (error) {
  if (error instanceOf mongoose.Document.ValidationError ) {
    console.log(error.errors['username'].message)
  }
}

Answer 2

To get rid of the initial string , you could simply use a split method on the string returned before displaying it. Here is a sample code:

let stringa = "User validation failed: username: Usernames must be 3 to 16 characters long and contain only alphanumeric characters and underscores (_)."; //replace this with error message
let stringb = (stringa.split(":")[2]);

console.log(stringb);//This displays the needed output string with Usernames 

Answer 3

Your error object has another nested object called properties that has a field called message. (example: properties.message) This gives you the exact string you wrote in the mongoose schema