Use Case: Reading a Record List

Input

Consider the following XML:

<Data>
  <Record>
    <Id>1</Id>
    <Name>John Doe</Name>
  </Record>
  <!-- ... millions of records, same structure ...-->
</Data>

Problem

The main goal is to transfrorm xmlSource, a readable utf8 bytes stream representing the input xml, into records: a stream of objects like

//...
{
  Id: "1",
  Name: "John Doe",
}
//...

Basic Solution

const {XMLReader, XMLNode} = require ('xml-toolkit')

const records = new XMLReader ({

  filterElements : 'Record', 

  map            : XMLNode.toObject ()

}).process (xmlSource)

// await someLoader.load (records)

Explanation

Here:

• an XMLReader is created;
  • with the filterElements that tells him to only handle Record elements (skipping the root Data node);
  • and the map option requiring the XMLNode.toObject transformation;
• the process method implicitly creates an XMLLexer instance, performs all the necessary piping and produces the desired object mode readable stream.

Q&A

How to alter field names?

With XMLNode.toObject's getName option. For example, by setting

map: XMLNode.toObject ({
  getName: s => s.toLowerCase (),
  //...
},

we'll obtain {id: "1", name: "John Doe"} instead of {Id: "1", Name: "John Doe"}.

How to adjust records content?

With XMLNode.toObject's map option. For example, by setting

map: XMLNode.toObject ({
  map: r => {...r, ord: ++ord}
  //...
},

we'll add the record counter named ord.