SaxesStream

NodeJS Streams wrapper around SaxesParser (npm package saxes)

• Single event stream
• Pipable to other streams
• TypeScript declarations

API

Input

Any string/Buffer Saxes would accept.

Output chunk format:

import { SaxesTag } from "saxes";

export type SaxesStreamChunk =
  { event: "opentag", path: string, tag: SaxesTag } |
  { event: "text", path: string, text: string } |
  { event: "closetag", path: string, tag: SaxesTag };

Events

Standard NodeJS Streams events.

Example 1 - Get huge online XML of books and stream parse it into CSV

import { SaxesOptions, SaxesStream, SaxesStreamChunk } from "saxes-stream";

import { Transform, TransformOptions, TransformCallback } from "stream";
import request from "request";
import fs from "fs";
import stringify from "csv-stringify";


/* Source HTTP XML stream */
const httpStream = request(url);


/* SaxesStream XML parser */
const const saxesOptions: SaxesOptions = {
  // ...
}

const streamOptions: TransformOptions = {
  // ...
}

const parser = new SaxesStream(saxesOptions, streamOptions);


/* Custom Transform Stream to pick the data from XML */
class BookTransform extends Transform {

  item: any = {};

  // Stream setting 
  readableObjectMode = true;
  writableObjectMode = true;

  _transform(chunk: SaxesStreamChunk, encoding: string, callback: TransformCallback) {

    /* Save parts by matching path */
    if (chunk.event === "text") {
      switch (chunk.path) {
        case ".books.book.title": this.item["title"] = chunk.text; break;
        case ".books.book.content": this.item["content"] = chunk.text; break;
      }
    }

    /* On ending </book> tag emit the completed book object as data (or piped to a next stream) */
    if (chunk.event === "closetag") {
      switch (chunk.path) {
        case ".books.book":
          this.push(this.item); 
          this.item = {};
          break;
      }
    }

    callback();

  }

}

const bookTransform = new BookTransform();


/* JSON -> CSV Transform Stream */
const csv = stringify({ delimiter: ',' });


/* File Write Stream */
const file = fs.createWriteStream('./books.csv');


/* PIPE ALL THINGS TOGETHER */
httpStream.pipe(parser).pipe(bookTransform).pipe(csv).pipe(file);