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std/csv/csv_stringify_stream.ts

The Deno Standard Library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.import { stringify } from "./stringify.ts";
/** Options for {@linkcode CsvStringifyStream}. */export interface CsvStringifyStreamOptions { /** * Delimiter used to separate values. * * @default {","} */ readonly separator?: string;
/** * A list of columns to be included in the output. * * If you want to stream objects, this option is required. */ readonly columns?: Array<string>;}
/** * Convert each chunk to a CSV record. * * @example * ```ts * import { CsvStringifyStream } from "https://deno.land/std@$STD_VERSION/csv/csv_stringify_stream.ts"; * * const file = await Deno.open("data.csv", { create: true, write: true }); * const readable = ReadableStream.from([ * { id: 1, name: "one" }, * { id: 2, name: "two" }, * { id: 3, name: "three" }, * ]); * * await readable * .pipeThrough(new CsvStringifyStream({ columns: ["id", "name"] })) * .pipeThrough(new TextEncoderStream()) * .pipeTo(file.writable); * ```` */export class CsvStringifyStream<TOptions extends CsvStringifyStreamOptions> extends TransformStream< TOptions["columns"] extends Array<string> ? Record<string, unknown> : Array<unknown>, string > { /** Construct a new instance. */ constructor(options?: TOptions) { const { separator, columns = [], } = options ?? {};
super( { start(controller) { if (columns && columns.length > 0) { try { controller.enqueue( stringify([columns], { separator, headers: false }), ); } catch (error) { controller.error(error); } } }, transform(chunk, controller) { try { controller.enqueue( stringify([chunk], { separator, headers: false, columns }), ); } catch (error) { controller.error(error); } }, }, ); }}