xml-streamer

xml-streamer

Motivation

You use Node.js for speed? You process XML streams? Then you want the fastest XML to JS parser: xml-streamer, based on node-expat and It implements the Node.js stream.Transform API.

Install

npm install xml-streamer

Basic Usage

xml-streamer can be used in four ways

// 1. By passing the resourcePath and reading data by calling `read` method instead listening for data events.

(function () {
  "use strict";

  var Parser = require('xml-streamer')
  
  var opts = {resourcePath: '/items/item'}

  var parser = new Parser(opts)
  
  parser.on('end', function () {
    // parsing ended no more data events will be raised
  })

  parser.on('error', function (error) {
    // error occurred
    // NOTE: when error event emitted no end event will be emitted
    console.error(error)
  })

  xmlStream.pipe(parser) // pipe your input xmlStream to parser.
  // readable
  parser.on('readable', function () {
     // if you don't want to consume "data" on "data" events you can wait for readable event and consume data by calling parser.read() 
  })
  // after readable event occured you can call read method and get data.
  parser.read() // will return one object at a time.
}())

// 2. By listening for interested nodes.

(function () {
  "use strict";

  var Parser = require('xml-streamer')
  
  var opts = {} // see `Available Constructor Options` section below.

  var parser = new Parser(opts)
  
  parser.on('item', function (item) {
    // consume the item object here
  })
  
  parser.on('end', function () {
    // parsing ended no more data events will be raised
  })

  parser.on('error', function (error) {
    // error occurred
    // NOTE: when error event emitted no end event will be emitted
    console.error(error)
  })

  xmlStream.pipe(parser) // pipe your input xmlStream to parser.
  // readable
  parser.on('readable', function () {
      // if you don't want to consume "data" on "data" events you can wait for readable event and consume data by calling parser.read() 
  })
}())

// 3. By passing a resource path.

(function () {
  "use strict";

  var Parser = require('xml-streamer')
  var opts = {resourcePath: '/items/item'}
  
  var parser = new Parser(opts)
  
  parser.on('data', function (data) {
    // consume the data object here
  })
  
  parser.on('end', function () {
    // parsing ended no more data events will be raised
  })

  parser.on('error', function (error) {
    // error occurred
    // NOTE: when error event emitted no end event will be emitted
    console.error(error)
  })

  xmlStream.pipe(parser) // pipe your input xmlStream to parser.
  // readable
  parser.on('readable', function () {
      // if you don't want to consume "data" on "data" events you can wait for readable event and consume data by calling parser.read() 
  })
}())

// 4. By passing a string or buffer to parse function

(function () {
  "use strict";

  var Parser = require('xml-streamer')
  
  var opts = {resourcePath: '/items/item'} // resourcePath is manditory when using parse method

  var parser = new Parser(opts)
  
  parser.parse(stringOrBuffer, function (err, data) {
    // consume data here
  })
}())

API

• #on('readable' function () {})
• #on('end' function () {}) Note: No end event will be emmited when error is emitted
• #on('error' function (err) {})
• #on('nodeName' function (err) {}) //if you are interested to listen on the "nodeName" instead of "data"
• #stop() pauses
• #resume() resumes
• #read() returns object if stream is readable

Available Constructor Options

• resourcePath: Type: String Optional field. Used to extract the XML nodes that you are interested in.

        // Ex: let the XML be
            ```xml
                <?xml version="1.0" encoding="utf-8"?>
                <items>
                    <item id="1" test= 'hello'>
                        <subitem sub= "TESTING SUB">one</subitem>
                        <subitem sub= "2">two</subitem>
                    </item>
                    <item id="2">
                        <subitem>three</subitem>
                        <subitem>four</subitem>
                        <subitem>five</subitem>
                    </item>
                </items>
            ```
       if you are interested in `item` nodes then resourcePath would be: `/items/item`
       if you are interested in `subitem` nodes then resourcePath would be: `/items/item/subitem`
       if you are interested in `items` nodes then resourcePath would be: `/items`
  

• emitOnNodeName: Type: Boolean Optional field. Set this to true if you want to listen on node names instead of data event. default: false

        // Ex: consider the above XML snippet
         ```javascript
            if you are interested in `item` nodes. You can listen for `data` event by default to get those nodes in JS object form
                    
                      parser.on('data', function (data) {
                         // item nodes as javascipt objects
                      })
  
            or else you can set `emitOnNodeName: true` and listen on node names like
  
                      parser.on('item', function (data) {
                         // item nodes as javascipt objects
                      })
         ```
  
            `NOTE:` when you set `emitOnNodeName:true` "data" events are emitted normally. So make sure you don't listen for both the events.
  

• attrsKey: Type: String Optional field. pass the value with which you want to reference attributes of a node in its object form. default: '$'

• textKey: Type: String Optional field. pass the value with which you want to reference node value in its object form. default: '_'

               // In the above XML snippet `subitem` node will look like this after converted to javascript object
              ```javascript
                      {
                          "$": {
                              "sub": "TESTING SUB"
                          }
                          "_": "one"
                      }
                      // if you want like this
                      {
                          "attrs": {
                              "sub": "TESTING SUB"
                          },
                          "text": "one"
                      }
              ```
                 // Then set `attrsKey= "attrs"` and `textKey= "text"`
  

• explicitArray: Type: Boolean Optional field. Default value is true. All children nodes will come in an array when this option is true.

        // Ex: For example let the XML be
            ```xml
                <?xml version="1.0" encoding="utf-8"?>
                <items>
                    <item id="1" test= 'hello'>
                        <subitem sub= "2">two</subitem>
                    </item>
                </items>
            ```
        // if explicitArray is true and resourcePath is /items/item. 
        // Output for above xml will be
            ```javascript
                    [
                       { '$': { id: '1', test: 'hello' },
                         subitem: { '$': { sub: '2' }, _: 'two' } },
                    ]
            ```
    `caution:` When explicitArray set to false and if there are multiple children nodes with same name then last node will override all preceding nodes. 
  

• verbatimText: Type: Boolean Optional field. Default value is false. When set, text attribute will include all blanks found in xml. When unset, blanks are removed as long as they come in one expat single block (blank lines, newlines and entities).

        // Ex: For example let the XML be
            ```xml
                <?xml version="1.0" encoding="utf-8"?>
                <items>
                    <item>
            This is
            a test
                    </item>
                </items>
            ```
        // if verbatimText is true and resourcePath is /items/item.
        // Output for above xml will be
            ```javascript
                    [
                       { '_' : "\nThis is\na test\n            "}
                    ]
            ```
  
        // if verbatimText is false and resourcePath is /items/item.
        // Output for above xml will be
            ```javascript
                    [
                       { '_' : "This isa test"}
                    ]
            ```
  

upcoming features

1. handling of compressed streams
2. handling of different encodings
3. Filtering of objects extracted from resourcePath based on xpaths and json paths

Namespace handling

A word about special parsing of xmlns: Note that "resourcePath" in the options is not an XPATH. So the value given to the resourcePath is treated as simple value and no expression evaluations are done.

Benchmark

xml-streamer internally uses node-expat

npm run benchmark

module	ops/sec	native	XML compliant	stream
sax-js	99,412	☐	☑	☑
node-xml	130,631	☐	☑	☑
libxmljs	276,136	☑	☑	☐
node-expat	322,769	☑	☑	☑

Higher is better.

Testing

npm install -g standard
npm test