Custom Error Messages

String form (all errors)

Override all validation errors with a single message.


const schema = new SchemaBuilder()
  .string()
  .minLength(5)
  .maxLength(20)
  .pattern("^[a-z]+$")
  .errorMessage("Username must be 5-20 lowercase letters")
  .build();
// ANY failure returns: "Username must be 5-20 lowercase letters"

Object form (per-keyword)


const schema = new SchemaBuilder()
  .string()
  .minLength(5)
  .maxLength(20)
  .pattern("^[a-z]+$")
  .errorMessage({
    type: "Must be text",
    minLength: "Too short - need at least 5 characters",
    maxLength: "Too long - maximum 20 characters",
    pattern: "Only lowercase letters allowed",
  })
  .build();

Property-level error messages


const schema = new SchemaBuilder()
  .object()
  .properties({
    email: (s) => s.string().format("email"),
    age: (s) => s.integer().minimum(18),
  })
  .errorMessage({
    properties: {
      email: "Please enter a valid email address",
      age: "You must be at least 18 years old",
    },
  })
  .build();

Per-keyword property errors


const schema = new SchemaBuilder()
  .object()
  .properties({
    email: (s) => s.string().format("email").minLength(5),
    password: (s) => s.string().minLength(8).pattern("^(?=.*[A-Z])"),
  })
  .errorMessage({
    properties: {
      email: {
        format: "Invalid email format",
        minLength: "Email too short",
      },
      password: {
        minLength: "Password must be at least 8 characters",
        pattern: "Password must contain an uppercase letter",
      },
    },
  })
  .build();

Nested schema error messages


const schema = new SchemaBuilder()
  .object()
  .properties({
    user: (s) =>
      s
        .object()
        .properties({
          name: (s) => s.string().minLength(2),
          email: (s) => s.string().format("email"),
        })
        .errorMessage({
          properties: {
            name: "Name must be at least 2 characters",
            email: "Invalid email",
          },
        }),
  })
  .build();

The _jetError fallback

Use _jetError as a catch-all for keywords without explicit messages.


const schema = new SchemaBuilder()
  .object()
  .properties({
    user: (s) =>
      s.object().properties({
        name: (s) => s.string(),
        email: (s) => s.string(),
      }),
  })
  .errorMessage({
    properties: {
      user: {
        _jetError: "User validation failed", // fallback
        properties: {
          name: "Invalid name",
          email: "Invalid email",
        },
      },
    },
  })
  .build();

For the full model of how error messages resolve, see the Jet-Validator Error Handling docs .