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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
/** Options for {@linkcode JsonStringifyStream}. */export interface StringifyStreamOptions {  /**   * Prefix to be added after stringify.   *   * @default {""}   */  readonly prefix?: string;  /**   * Suffix to be added after stringify.   *   * @default {"\n"}   */  readonly suffix?: string;  /**   * Controls the buffer of the {@linkcode TransformStream} used internally.   *   * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/TransformStream/TransformStream#writablestrategy}   */  readonly writableStrategy?: QueuingStrategy<unknown>;  /**   * Controls the buffer of the {@linkcode TransformStream} used internally.   *   * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/TransformStream/TransformStream#readablestrategy}   */  readonly readableStrategy?: QueuingStrategy<string>;}
/** * Convert each chunk to JSON string. * * This can be used to stringify {@link https://jsonlines.org/ | JSON lines}, * {@link https://ndjson.org/ | NDJSON}, * {@link https://datatracker.ietf.org/doc/html/rfc7464 | JSON Text Sequences}, * and {@link https://en.wikipedia.org/wiki/JSON_streaming#Concatenated_JSON | Concatenated JSON}. * * You can optionally specify a prefix and suffix for each chunk. The default prefix is `""` and the default suffix is `"\n"`. * * @example * ```ts * import { JsonStringifyStream } from "https://deno.land/std@$STD_VERSION/json/json_stringify_stream.ts"; * * const file = await Deno.open("./tmp.jsonl", { create: true, write: true }); * * ReadableStream.from([{ foo: "bar" }, { baz: 100 }]) *   .pipeThrough(new JsonStringifyStream()) // convert to JSON lines (ndjson) *   .pipeThrough(new TextEncoderStream()) // convert a string to a Uint8Array *   .pipeTo(file.writable) *   .then(() => console.log("write success")); * ``` * * @example * To convert to [JSON Text Sequences](https://datatracker.ietf.org/doc/html/rfc7464), set the * prefix to the delimiter "\x1E" as options. * ```ts * import { JsonStringifyStream } from "https://deno.land/std@$STD_VERSION/json/json_stringify_stream.ts"; * * const file = await Deno.open("./tmp.jsonl", { create: true, write: true }); * * ReadableStream.from([{ foo: "bar" }, { baz: 100 }]) *   .pipeThrough(new JsonStringifyStream({ prefix: "\x1E", suffix: "\n" })) // convert to JSON Text Sequences *   .pipeThrough(new TextEncoderStream()) *   .pipeTo(file.writable) *   .then(() => console.log("write success")); * ``` * * @example * If you want to stream [JSON lines](https://jsonlines.org/) from the server: * ```ts * import { JsonStringifyStream } from "https://deno.land/std@$STD_VERSION/json/json_stringify_stream.ts"; * * // A server that streams one line of JSON every second * Deno.serve(() => { *   let intervalId: number | undefined; *   const readable = new ReadableStream({ *     start(controller) { *       // enqueue data once per second *       intervalId = setInterval(() => { *         controller.enqueue({ now: new Date() }); *       }, 1000); *     }, *     cancel() { *       clearInterval(intervalId); *     }, *   }); * *   const body = readable *     .pipeThrough(new JsonStringifyStream()) // convert data to JSON lines *     .pipeThrough(new TextEncoderStream()); // convert a string to a Uint8Array * *   return new Response(body); * }); * ``` */export class JsonStringifyStream extends TransformStream<unknown, string> {  /** Constructs new instance. */  constructor({    prefix = "",    suffix = "\n",    writableStrategy,    readableStrategy,  }: StringifyStreamOptions = {}) {    super(      {        transform(chunk, controller) {          controller.enqueue(`${prefix}${JSON.stringify(chunk)}${suffix}`);        },      },      writableStrategy,      readableStrategy,    );  }}