@loopback/docs
Version:
Documentation files rendered at [https://loopback.io](https://loopback.io)
29 lines (23 loc) • 2.27 kB
Markdown
lang: en
title: Error Codes
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI, Error Handling
sidebar: lb4_sidebar
permalink: /doc/en/lb4/Error-codes.html
redirect_from: /doc/en/lb4/Error-handling.html
In order to allow clients to reliably detect individual error causes, LoopBack
sets the error `code` property to a machine-readable string.
| Error code | Description |
| :------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| ENTITY_NOT_FOUND | The entity (model) was not found. This error is returned for example by [`EntityCrudRepository.prototype.findById`](https://loopback.io/doc/en/lb4/apidocs.repository.entitycrudrepository.findbyid.html) |
| VALIDATION_FAILED | The data provided by the client is not a valid entity. |
| INVALID_PARAMETER_VALUE | The value provided for a parameter of a REST endpoint is not valid. For example, a string value was provided for a numeric parameter. |
| MISSING_REQUIRED_PARAMETER | No value was provided for a required parameter. |
Besides LoopBack-specific error codes, your application can encounter low-level
error codes from Node.js and the underlying operating system. For example, when
a connector is not able to reach the database, an error with code `ECONNREFUSED`
is returned.
See the following resources for a list of low-level error codes:
- [Common System Errors](https://nodejs.org/api/errors.html#errors_common_system_errors)
- [Node.js Error Codes](https://nodejs.org/api/errors.html#errors_node_js_error_codes)