streamingjsxmlparser

An efficient XML parser for JS. Implements part of the XML specification.

• Streaming: This algorithmic optimization makes it several times faster than a typical XML parser.

Rationale: This parser does not build a tree, which causes memory allocation and creates GC pressure. Instead, it parses in a stream, looking at it character-by-character. Modern superscalar CPUs are very efficient at those types of operations.

How to use it

Streaming APIs are used by building an internal state and collecting information as you traverse the tree.

Example

import { XMLParser } from './xmlparser.mjs'
class MyParser extends XMLParser {
  emitData(data) {
     console.log("Encountered data:", JSON.stringify(data))
     this.data = '' // mark data as processed
  }
  emitStartTag(name, attributes) {
     console.log("Encountered a start tag:", name, attributes)
  }
  emitEndTag(name) {
     console.log("Encountered an end tag:", name)
  }
}

Results in:

Encountered a start tag: html {}
Encountered a start tag: head {}
Encountered a start tag: title {}
Encountered data: "Test"
Encountered an end tag: title
Encountered an end tag: head
Encountered data: "\n            "
Encountered a start tag: body {}
Encountered a start tag: h1 { key: 'value' }
Encountered data: "This is a heading!"
Encountered an end tag: h1
Encountered an end tag: body
Encountered an end tag: html

Tips and tricks

Using a streaming parser is like writing a for loop over all events.

Warning

This is not an HTML parser. HTML is more complex, because it supports features such as:

• Self-closing tags: <p>a<p>b turns into <p>a</p><p>b</p> because p is a self-closing tag.
• Quoteless attributes: <h1 class=heading> works as well as <h1 class="heading">.