# Node.js Scripts

For tasks that go beyond CLI piping — complex logic, external API integration, scheduled jobs — write a Node.js script with `bkper-js`.

## Setup

```bash
# Create a script project
mkdir my-bkper-script && cd my-bkper-script
npm init -y
npm install bkper-js bkper
```

Authenticate once via the CLI:

```bash
bkper auth login
```

## The pattern

Every script follows the same structure: authenticate, get a book, do work.

```ts
import { Bkper } from 'bkper-js';
import { getOAuthToken } from 'bkper';

Bkper.setConfig({
    oauthTokenProvider: async () => getOAuthToken(),
});

const bkper = new Bkper();
const book = await bkper.getBook('your-book-id');

// Your logic here
```

### Export balances to JSON

```ts
import { Bkper } from 'bkper-js';
import { getOAuthToken } from 'bkper';
import { writeFileSync } from 'fs';

Bkper.setConfig({
    oauthTokenProvider: async () => getOAuthToken(),
});

const bkper = new Bkper();
const book = await bkper.getBook('your-book-id');

const report = await book.getBalancesReport('on:2025-12-31');
const rows = report.getBalancesContainers().map(container => ({
    name: container.getName(),
    balance: container.getCumulativeBalance().toString(),
}));

writeFileSync('balances.json', JSON.stringify(rows, null, 2));
console.log(`Exported ${rows.length} balances`);
```

### Bulk-create accounts from a JSON export

```ts
import { Account, Bkper } from 'bkper-js';
import { getOAuthToken } from 'bkper';
import { readFileSync } from 'fs';

type AccountInput = {
    name: string;
    type: 'ASSET' | 'LIABILITY' | 'INCOMING' | 'OUTGOING';
    groups?: Array<{ id?: string; name?: string }>;
};

Bkper.setConfig({
    oauthTokenProvider: async () => getOAuthToken(),
});

const bkper = new Bkper();
const book = await bkper.getBook('your-book-id');

const data: AccountInput[] = JSON.parse(readFileSync('accounts.json', 'utf-8'));

const accounts = data.map(acc => {
    const account = new Account(book).setName(acc.name).setType(acc.type);
    if (acc.groups?.length) {
        account.setGroups(acc.groups);
    }
    return account;
});

const created = await book.batchCreateAccounts(accounts);
console.log(`Created ${created.length} accounts`);
```

### Query transactions and generate a report

```ts
import { Amount, Bkper } from 'bkper-js';
import { getOAuthToken } from 'bkper';

Bkper.setConfig({
    oauthTokenProvider: async () => getOAuthToken(),
});

const bkper = new Bkper();
const book = await bkper.getBook('your-book-id');

const result = await book.listTransactions('account:Expenses after:2025-01-01');

let total = new Amount(0);
for (const tx of result.getItems()) {
    const amount = tx.getAmount();
    if (!amount) continue;

    total = total.plus(amount);
    console.log(`${tx.getDate()} | ${tx.getDescription()} | ${amount.toString()}`);
}
console.log(`\nTotal: ${total.toString()}`);
```

### With cron

```bash
# Run daily at 8am
0 8 * * * cd /path/to/script && node export.mjs
```

### In CI environments

The CLI helper `getOAuthToken()` is designed for local developer machines, where the CLI can store and refresh credentials. In GitHub Actions or other unattended environments, provide your own token source:

```ts
import { Bkper } from 'bkper-js';

const bkper = new Bkper({
    oauthTokenProvider: async () => {
        const token = process.env.BKPER_OAUTH_TOKEN;
        if (!token) {
            throw new Error('BKPER_OAUTH_TOKEN is not set');
        }
        return token;
    },
});
```

Use this pattern only when another system is already issuing and rotating the token for the job. For unattended long-running automation, implement your own OAuth flow instead of relying on the CLI's locally stored credentials.

## Error handling

Wrap API calls with proper error handling:

```ts
import { BkperError } from 'bkper-js';

try {
    const book = await bkper.getBook('your-book-id');
    // ...
} catch (error) {
    if (error instanceof BkperError && error.code === 404) {
        console.error('Book not found');
    } else if (error instanceof BkperError && error.code === 403) {
        console.error('No access to this book');
    } else if (error instanceof Error) {
        console.error('API error:', error.message);
    } else {
        console.error('Unknown error:', String(error));
    }
    process.exit(1);
}
```

## When to use scripts vs apps

| Scenario                                       | Use                                       |
| ---------------------------------------------- | ----------------------------------------- |
| One-off data migration                         | Script                                    |
| Scheduled export/report                        | Script                                    |
| Reacting to book events in real time           | [Platform app](http://bkper.com/docs/build/apps/overview.md) |
| Custom UI for users                            | [Platform app](http://bkper.com/docs/build/apps/overview.md) |
| Complex multi-step workflow with external APIs | Script or app, depending on trigger       |

## Next steps

- [bkper-js API Reference](http://bkper.com/docs/api/bkper-js.md) — Full SDK documentation
- [CLI Scripting & Piping](http://bkper.com/docs/build/scripts/cli-pipelines.md) — For simpler tasks, the CLI may be enough
- [Direct API Usage](http://bkper.com/docs/build/scripts/rest-api.md) — Use the REST API from any language