fake-readable-stream.js

const fs = require("fs");
const stream = fs.createWriteStream("./fake-read-stream");

const fakeReadableStream = new (class {
  readable = true;

  constructor() {
    this.data =
      "abc ewij fj wiefj ewi tj94htr834h u4 hru4 u9jr92i3 i09rj 239ij erw9i fgj3u94it 34i9 tj";
    this.cursor = 0;
    this.mode = "pull";
    this.listeners = [];
    this.ended = false;
  }
  on(type, f) {
    if (type === "data") {
      this.listeners.push({ type: "data", handler: f });

      setTimeout(async () => {
        this.mode = "push";
        let r;
        while (((r = this.read()), this.mode === "push")) {
          const r = this.read();
          this.listeners
            .filter(({ type }) => type === "data")
            .forEach(({ handler }) => f("data", r));
          await new Promise((res) => setTimeout(res));
        }
      });
    } else if (type === "end") {
      this.listeners.push({ type: "end", handler: f });
    }
  }
  read() {
    if (this.cursor === this.data.length) {
      this.mode = "pull";
      if (!this.ended) {
        this.ended = true;
        this.listeners
          .filter(({ type }) => type === "end")
          .forEach((f) => f("end", null));
      }
      return null;
    }
    this.mode = "push";
    return this.data[this.cursor++];
  }
  pipe(writableStream) {
    (async () => {
      let r;
      while (((r = this.read()), this.mode === "push")) {
        writableStream.write(Buffer.from(r));
        await new Promise((res) => setTimeout(res));
      }
      writableStream.end();
    })();
  }
})();

// ???

fakeReadableStream.pipe(stream);