# Autocompletion & Typings

{% hint style="success" %}
This is the official documentation of the `@forestadmin/agent` Node.js agent.
{% endhint %}

Since the Forest Admin agent is fully written in TypeScript, every function has autocompletion capabilities. The agent can generate typing files based on your models.

This allows:

* Autocompletion of collection names and fields
* Typing validation on all your handlers (when using TypeScript)

### Generate a typing file

The typing file generated by Forest Admin will allow you to autocomplete any given fields of a collection. This is an auto-generated file, so we highly suggest not editing it manually.

In the following sections, you can see that two options are given to the `createAgent` function:

* `typingsPath`: The location you want your typing file to be created.
* `typingsMaxDepth`: The maximum depth of introspection for relationships.

### Using the typing file in a TypeScript context

In a TypeScript context, the usage of the typing file is pretty straightforward. You can simply import the typing file and template your `createAgent` with the schema to use it.

{% tabs %}
{% tab title="agent.ts" %}

```typescript
import { createAgent } from '@forestadmin/agent';
import { Schema } from './typings';
import transactions from './customization/transactions';

await createAgent<Schema>({
  // ...
  typingsPath: './typings.ts',
  typingsMaxDepth: 5,
})
  .customizeCollection('transactions', transactions)
  .mountOnStandaloneServer(3000)
  .start();
```

{% endtab %}

{% tab title="customization/transactions.ts" %}

```typescript
import { CollectionCustomizer } from '@forestadmin/agent';
import { Schema } from '../typings';

export default (transactions: CollectionCustomizer<Schema, 'transactions'>) =>
  transactions.removeField('amountInEur');
```

{% endtab %}
{% endtabs %}

You should be able to see that the `customizeCollection` method is strongly typed, as well as the `transactions` handler.

### Using the typing file in a JavaScript context

You can still benefit from it in a JavaScript environment by using the JSDoc syntax.

If you choose to split your `customizeCollection` handler in a dedicated file (That's the project scaffolding we usually use at Forest Admin), you can use the following JSDoc example to keep the autocomplete experience intact.

{% tabs %}
{% tab title="agent.js" %}

```javascript
const { createAgent } = require('@forestadmin/agent');
const transactions = require('./customization/transactions');

/**
 * Importing the typing file to keep the autocompletion
 * @typedef {import('@forestadmin/agent').Agent} Agent
 * @typedef {import('../typings').Schema} Schema
 */

/**
 * @type {Agent<Schema>}
 */
const agent = createAgent({
  //...
  typingsPath: './typings.ts',
  typingsMaxDepth: 5,
});

await agent
  .customizeCollection('transactions', transactions)
  .mountOnStandaloneServer(3000)
  .start();
```

{% endtab %}

{% tab title="customization/transactions.js" %}

```javascript
/**
 * Importing the typing file to keep the autocompletion
 * @typedef {import('@forestadmin/agent').CollectionCustomizer} CollectionCustomizer
 * @typedef {import('../typings').Schema} Schema
 */

/**
 * @param {CollectionCustomizer<Schema, 'transactions'>} transactions
 */
module.exports = transactions => {
  // Autocompletion should be available here
  transactions.removeField('amountInEur');
};
```

{% endtab %}
{% endtabs %}