The JavaScript code reads a JSON file using a stream, transforms it into a Parquet format leveraging a defined schema, and then writes it to a Parquet file. The transformation utilizes the "parquetjs" library for Parquet format handling and "stream-json" for efficient JSON streaming, thereby converting a large JSON file to a Parquet file with specified schema mapping, which can be more efficient for storage and querying.

import { createReadStream, createWriteStream } from "fs";
import { ParquetSchema, ParquetTransformer } from "parquetjs";
import * as StreamArray from "stream-json/streamers/StreamArray";

const reader = createReadStream("data-json.json");
const destination = createWriteStream("countries.parquet");

const schema = new ParquetSchema({
  value: {
    fields: {
      Country: { type: "UTF8" },
      Indicator: { type: "UTF8" },
      Value: { type: "FLOAT" },
      Year: { type: "INT64" }

  .pipe(new ParquetTransformer(schema))