@prairielearn/csv

A few helpful wrappers on top of the functionality from csv-stringify.

Usage

Here's an example taking data from @prairielearn/postgres#queryCursor() and writing it to a file, though this should be applicable to any source and destination streams:

``ts
import { stringifyStream } from '@prairielearn/csv';
import { queryCursor } from '@prairielearn/postgres';
import { pipeline } from 'node:stream/promises';
import { createWriteStream } from 'node:fs';
import { IdSchema } from '@prairielearn/zod';
import { z } from 'zod';

const WorkspaceSchema = z.object({
id: IdSchema,
hostname: z.string(),
});
type Workspace = z.infer;

const cursor = await queryCursor('SELECT id, hostname FROM workspaces;', WorkspaceSchema);
const output = createWriteStream('workspaces.csv');

const stringifier = stringifyStream({
header: true,
columns: [
{ key: 'id', header: 'ID' },
{ key: 'hostname', header: 'Hostname' },
],
// Optionally provide a function to transform each item in the stream.
transform(record) {
return {
id: workspace-${record.id},
hostname: record.hostname,
};
},
});

await pipeline(cursor.stream(100), stringifier, output);
`

Note that this works best when the source stream is producing data asynchronously, such as though an async iterator. If you use a synchronous data source like Readable.from([...]), the conversion will still occur synchronously. If you have a large array of data in memory and want to convert it to a CSV, you can use stringifyNonblocking:

`ts
import { stringifyNonblocking } from '@prairielearn/csv';
import { createWriteStream } from 'node:fs';

const data = Array.from(new Array(100_000), (_, i) => ({ id: i }));
const output = createWriteStream('numbers.csv');
stringifyNonblocking<{ id: number }>(data, {
header: true,
columns: [{ key: 'id', header: 'ID' }],
}).pipe(output);
`

For lower-level usage, stringify and Stringifier are also re-exported from csv-stringify:

`ts
import { stringify, Stringifier } from '@prairielearn/csv';
``