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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
/** Optional object interface for `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 TransformStream used internally. Check https://developer.mozilla.org/en-US/docs/Web/API/TransformStream/TransformStream. */ readonly writableStrategy?: QueuingStrategy<unknown>; /** Controls the buffer of the TransformStream used internally. Check https://developer.mozilla.org/en-US/docs/Web/API/TransformStream/TransformStream. */ readonly readableStrategy?: QueuingStrategy<string>;}
/** * Convert each chunk to JSON string. * * This can be used to stringify [JSON lines](https://jsonlines.org/), [NDJSON](http://ndjson.org/), [JSON Text Sequences](https://datatracker.ietf.org/doc/html/rfc7464), and [Concatenated JSON](https://en.wikipedia.org/wiki/JSON_streaming#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@$STD_VERSION/json/json_stringify_stream.ts"; * * // A server that streams one line of JSON every second * Deno.serve(() => { * let intervalId: number | undefined; * const readable = new ReadableStream({ * start(controller) { * // enqueue data once per second * intervalId = setInterval(() => { * controller.enqueue({ now: new Date() }); * }, 1000); * }, * cancel() { * clearInterval(intervalId); * }, * }); * * const body = readable * .pipeThrough(new JsonStringifyStream()) // convert data to JSON lines * .pipeThrough(new TextEncoderStream()); // convert a string to a Uint8Array * * return new Response(body); * }); * ``` */export class JsonStringifyStream extends TransformStream<unknown, string> { constructor({ prefix = "", suffix = "\n", writableStrategy, readableStrategy, }: StringifyStreamOptions = {}) { super( { transform(chunk, controller) { controller.enqueue(`${prefix}${JSON.stringify(chunk)}${suffix}`); }, }, writableStrategy, readableStrategy, ); }}