undeexcepturi/docs/versioned_docs/version-4.5/debugging.md

TypeScript ORM for Node.js based on Data Mapper, Unit of Work and Identity Map patterns. Supports MongoDB, MySQL, PostgreSQL and SQLite databases as well as usage with vanilla JavaScript.

---
title: Logging
---

For development purposes it might come handy to enable logging and debug mode:

```typescript
return MikroORM.init({
  debug: true,
});
```

By doing this `MikroORM` will start using `console.log()` function to dump all queries:

```
[query] select `e0`.* from `author` as `e0` where `e0`.`name` = ? limit ? [took 2 ms]
[query] begin [took 1 ms]
[query] insert into `author` (`name`, `email`, `created_at`, `updated_at`, `terms_accepted`) values (?, ?, ?, ?, ?) [took 2 ms]
[query] commit [took 2 ms]
```

It is also useful for debugging problems with entity discovery, as you will see information about every processed entity:

```
[discovery] ORM entity discovery started
[discovery] - processing entity Author
[discovery] - using cached metadata for entity Author
[discovery] - processing entity Book
[discovery] - processing entity BookTag
[discovery] - entity discovery finished after 13 ms
```

## Custom Logger

You can also provide your own logger via `logger` option.

```typescript
return MikroORM.init({
  debug: true,
  logger: msg => myCustomLogger.log(msg),
});
```

## Logger Namespaces

There are multiple Logger Namespaces that you can specifically request, while omitting the rest. Just specify array of them via the `debug` option:

```typescript
return MikroORM.init({
  debug: ['query'], // now only queries will be logged
});
```

Currently, there are 4 namespaces – `query`, `query-params`, `discovery` and `info`.

If you provide `query-params` then you must also provide `query` in order for it to take effect.

## Highlighters

Previously Highlight.js was used to highlight various things in the CLI, like SQL and mongo queries, or migrations or entities generated via CLI. While the library worked fine, it was causing performance issues mainly for those bundling via webpack and using lambdas, as the library was huge.

In v4 highlighting is disabled by default, and there are 2 highlighters you can optionally use (you need to install them first).

```typescript
import { SqlHighlighter } from '@mikro-orm/sql-highlighter';

MikroORM.init({
  highlighter: new SqlHighlighter(),
  // ...
});
```

For MongoDB you can use `MongoHighlighter` from `@mikro-orm/mongo-highlighter` package.