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:

1import { SaxesTag } from "saxes";
2
3export type SaxesStreamChunk =
4  { event: "opentag", path: string, tag: SaxesTag } |
5  { event: "text", path: string, text: string } |
6  { 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

1
2import { SaxesOptions, SaxesStream, SaxesStreamChunk } from "saxes-stream";
3
4import { Transform, TransformOptions, TransformCallback } from "stream";
5import request from "request";
6import fs from "fs";
7import stringify from "csv-stringify";
8
9
10/* Source HTTP XML stream */
11const httpStream = request(url);
12
13
14/* SaxesStream XML parser */
15const const saxesOptions: SaxesOptions = {
16  // ...
17}
18
19const streamOptions: TransformOptions = {
20  // ...
21}
22
23const parser = new SaxesStream(saxesOptions, streamOptions);
24
25
26/* Custom Transform Stream to pick the data from XML */
27class BookTransform extends Transform {
28
29  item: any = {};
30
31  // Stream setting 
32  readableObjectMode = true;
33  writableObjectMode = true;
34
35  _transform(chunk: SaxesStreamChunk, encoding: string, callback: TransformCallback) {
36
37    /* Save parts by matching path */
38    if (chunk.event === "text") {
39      switch (chunk.path) {
40        case ".books.book.title": this.item["title"] = chunk.text; break;
41        case ".books.book.content": this.item["content"] = chunk.text; break;
42      }
43    }
44
45    /* On ending </book> tag emit the completed book object as data (or piped to a next stream) */
46    if (chunk.event === "closetag") {
47      switch (chunk.path) {
48        case ".books.book":
49          this.push(this.item); 
50          this.item = {};
51          break;
52      }
53    }
54
55    callback();
56
57  }
58
59}
60
61const bookTransform = new BookTransform();
62
63
64/* JSON -> CSV Transform Stream */
65const csv = stringify({ delimiter: ',' });
66
67
68/* File Write Stream */
69const file = fs.createWriteStream('./books.csv');
70
71
72/* PIPE ALL THINGS TOGETHER */
73httpStream.pipe(parser).pipe(bookTransform).pipe(csv).pipe(file);
74
75