node-xml2js

by Leonidas-from-XIV

Leonidas-from-XIV / node-xml2js

XML to JavaScript object converter.

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node-xml2js

Ever had the urge to parse XML? And wanted to access the data in some sane, easy way? Don't want to compile a C parser, for whatever reason? Then xml2js is what you're looking for!

Description

Simple XML to JavaScript object converter. It supports bi-directional conversion. Uses sax-js and xmlbuilder-js.

Note: If you're looking for a full DOM parser, you probably want JSDom.

Installation

Simplest way to install

xml2js
is to use npm, just
npm
install xml2js
which will download xml2js and all dependencies.

xml2js is also available via Bower, just

bower install
xml2js
which will download xml2js and all dependencies.

Usage

No extensive tutorials required because you are a smart developer! The task of parsing XML should be an easy one, so let's make it so! Here's some examples.

Shoot-and-forget usage

You want to parse XML as simple and easy as possible? It's dangerous to go alone, take this:

var parseString = require('xml2js').parseString;
var xml = "Hello xml2js!"
parseString(xml, function (err, result) {
    console.dir(result);
});

Can't get easier than this, right? This works starting with

xml2js
0.2.3. With CoffeeScript it looks like this:
{parseString} = require 'xml2js'
xml = "Hello xml2js!"
parseString xml, (err, result) ->
    console.dir result

If you need some special options, fear not,

xml2js
supports a number of options (see below), you can specify these as second argument:
parseString(xml, {trim: true}, function (err, result) {
});

Simple as pie usage

That's right, if you have been using xml-simple or a home-grown wrapper, this was added in 0.1.11 just for you:

var fs = require('fs'),
    xml2js = require('xml2js');

var parser = new xml2js.Parser(); fs.readFile(__dirname + '/foo.xml', function(err, data) { parser.parseString(data, function (err, result) { console.dir(result); console.log('Done'); }); });

Look ma, no event listeners!

You can also use

xml2js
from CoffeeScript, further reducing the clutter:
fs = require 'fs',
xml2js = require 'xml2js'

parser = new xml2js.Parser() fs.readFile __dirname + '/foo.xml', (err, data) -> parser.parseString data, (err, result) -> console.dir result console.log 'Done.'

But what happens if you forget the

new
keyword to create a new
Parser
? In the middle of a nightly coding session, it might get lost, after all. Worry not, we got you covered! Starting with 0.2.8 you can also leave it out, in which case
xml2js
will helpfully add it for you, no bad surprises and inexplicable bugs!

Promise usage

var xml2js = require('xml2js');
var xml = '';

// With parser var parser = new xml2js.Parser(/* options */); parser.parseStringPromise(data).then(function (result) { console.dir(result); console.log('Done'); }) .catch(function (err) { // Failed });

// Without parser xml2js.parseStringPromise(data /*, options */).then(function (result) { console.dir(result); console.log('Done'); }) .catch(function (err) { // Failed });

Parsing multiple files

If you want to parse multiple files, you have multiple possibilities:

  • You can create one
    xml2js.Parser
    per file. That's the recommended one and is promised to always just work.
  • You can call
    reset()
    on your parser object.
  • You can hope everything goes well anyway. This behaviour is not guaranteed work always, if ever. Use option #1 if possible. Thanks!

So you wanna some JSON?

Just wrap the

result
object in a call to
JSON.stringify
like this
JSON.stringify(result)
. You get a string containing the JSON representation of the parsed object that you can feed to JSON-hungry consumers.

Displaying results

You might wonder why, using

console.dir
or
console.log
the output at some level is only
[Object]
. Don't worry, this is not because
xml2js
got lazy. That's because Node uses
util.inspect
to convert the object into strings and that function stops after
depth=2
which is a bit low for most XML.

To display the whole deal, you can use

console.log(util.inspect(result, false,
null))
, which displays the whole result.

So much for that, but what if you use eyes for nice colored output and it truncates the output with

? Don't fear, there's also a solution for that, you just need to increase the
maxLength
limit by creating a custom inspector
var inspect = require('eyes').inspector({maxLength: false})
and then you can easily
inspect(result)
.

XML builder usage

Since 0.4.0, objects can be also be used to build XML:

var xml2js = require('xml2js');

var obj = {name: "Super", Surname: "Man", age: 23};

var builder = new xml2js.Builder(); var xml = builder.buildObject(obj);

will result in:

  Super
  Man
  23

At the moment, a one to one bi-directional conversion is guaranteed only for default configuration, except for

attrkey
,
charkey
and
explicitArray
options you can redefine to your taste. Writing CDATA is supported via setting the
cdata
option to
true
.

To specify attributes: ```javascript var xml2js = require('xml2js');

var obj = {root: {$: {id: "my id"}, _: "my inner text"}};

var builder = new xml2js.Builder(); var xml = builder.buildObject(obj);

will result in:
xml <?xml version="1.0" encoding="UTF-8" standalone="yes"?> my inner text ```

Adding xmlns attributes

You can generate XML that declares XML namespace prefix / URI pairs with xmlns attributes.

Example declaring a default namespace on the root element:

let obj = { 
  Foo: {
    $: {
      "xmlns": "http://foo.com"
    }   
  }
};  

Result of

buildObject(obj)
:
xml

Example declaring non-default namespaces on non-root elements:
javascript
let obj = {
  'foo:Foo': {
    $: {
      'xmlns:foo': 'http://foo.com'
    },
    'bar:Bar': {
      $: {
        'xmlns:bar': 'http://bar.com'
      }
    }
  }
}
Result of
buildObject(obj)
:
xml

  

Processing attribute, tag names and values

Since 0.4.1 you can optionally provide the parser with attribute name and tag name processors as well as element value processors (Since 0.4.14, you can also optionally provide the parser with attribute value processors):

function nameToUpperCase(name){
    return name.toUpperCase();
}

//transform all attribute and tag names and values to uppercase parseString(xml, { tagNameProcessors: [nameToUpperCase], attrNameProcessors: [nameToUpperCase], valueProcessors: [nameToUpperCase], attrValueProcessors: [nameToUpperCase]}, function (err, result) { // processed data });

The

tagNameProcessors
and
attrNameProcessors
options accept an
Array
of functions with the following signature:
function (name){
  //do something with `name`
  return name
}

The

attrValueProcessors
and
valueProcessors
options accept an
Array
of functions with the following signature:
function (value, name) {
  //`name` will be the node name or attribute name
  //do something with `value`, (optionally) dependent on the node/attr name
  return value
}

Some processors are provided out-of-the-box and can be found in

lib/processors.js
:
  • normalize
    : transforms the name to lowercase. (Automatically used when
    options.normalize
    is set to
    true
    )
  • firstCharLowerCase
    : transforms the first character to lower case. E.g. 'MyTagName' becomes 'myTagName'
  • stripPrefix
    : strips the xml namespace prefix. E.g
     will become 'Bar'.
    (N.B.: the 
    xmlns
    prefix is NOT stripped.)
  • parseNumbers
    : parses integer-like strings as integers and float-like strings as floats E.g. "0" becomes 0 and "15.56" becomes 15.56
  • parseBooleans
    : parses boolean-like strings to booleans E.g. "true" becomes true and "False" becomes false

Options

Apart from the default settings, there are a number of options that can be specified for the parser. Options are specified by

new Parser({optionName:
value})
. Possible options are:
  • attrkey
    (default:
    $
    ): Prefix that is used to access the attributes. Version 0.1 default was
    @
    .
  • charkey
    (default:
    _
    ): Prefix that is used to access the character content. Version 0.1 default was
    #
    .
  • explicitCharkey
    (default:
    false
    )
  • trim
    (default:
    false
    ): Trim the whitespace at the beginning and end of text nodes.
  • normalizeTags
    (default:
    false
    ): Normalize all tag names to lowercase.
  • normalize
    (default:
    false
    ): Trim whitespaces inside text nodes.
  • explicitRoot
    (default:
    true
    ): Set this if you want to get the root node in the resulting object.
  • emptyTag
    (default:
    ''
    ): what will the value of empty nodes be. In case you want to use an empty object as a default value, it is better to provide a factory function
    () => ({})
    instead. Without this function a plain object would become a shared reference across all occurrences with unwanted behavior.
  • explicitArray
    (default:
    true
    ): Always put child nodes in an array if true; otherwise an array is created only if there is more than one.
  • ignoreAttrs
    (default:
    false
    ): Ignore all XML attributes and only create text nodes.
  • mergeAttrs
    (default:
    false
    ): Merge attributes and child elements as properties of the parent, instead of keying attributes off a child attribute object. This option is ignored if
    ignoreAttrs
    is
    true
    .
  • validator
    (default
    null
    ): You can specify a callable that validates the resulting structure somehow, however you want. See unit tests for an example.
  • xmlns
    (default
    false
    ): Give each element a field usually called '$ns' (the first character is the same as attrkey) that contains its local name and namespace URI.
  • explicitChildren
    (default
    false
    ): Put child elements to separate property. Doesn't work with
    mergeAttrs = true
    . If element has no children then "children" won't be created. Added in 0.2.5.
  • childkey
    (default
    $$
    ): Prefix that is used to access child elements if
    explicitChildren
    is set to
    true
    . Added in 0.2.5.
  • preserveChildrenOrder
    (default
    false
    ): Modifies the behavior of
    explicitChildren
    so that the value of the "children" property becomes an ordered array. When this is
    true
    , every node will also get a
    #name
    field whose value will correspond to the XML nodeName, so that you may iterate the "children" array and still be able to determine node names. The named (and potentially unordered) properties are also retained in this configuration at the same level as the ordered "children" array. Added in 0.4.9.
  • charsAsChildren
    (default
    false
    ): Determines whether chars should be considered children if
    explicitChildren
    is on. Added in 0.2.5.
  • includeWhiteChars
    (default
    false
    ): Determines whether whitespace-only text nodes should be included. Added in 0.4.17.
  • async
    (default
    false
    ): Should the callbacks be async? This might be an incompatible change if your code depends on sync execution of callbacks. Future versions of
    xml2js
    might change this default, so the recommendation is to not depend on sync execution anyway. Added in 0.2.6.
  • strict
    (default
    true
    ): Set sax-js to strict or non-strict parsing mode. Defaults to
    true
    which is highly recommended, since parsing HTML which is not well-formed XML might yield just about anything. Added in 0.2.7.
  • attrNameProcessors
    (default:
    null
    ): Allows the addition of attribute name processing functions. Accepts an
    Array
    of functions with following signature:
    javascript
    function (name){
        //do something with `name`
        return name
    }
    
    Added in 0.4.14
  • attrValueProcessors
    (default:
    null
    ): Allows the addition of attribute value processing functions. Accepts an
    Array
    of functions with following signature:
    javascript
    function (value, name){
      //do something with `name`
      return name
    }
    
    Added in 0.4.1
  • tagNameProcessors
    (default:
    null
    ): Allows the addition of tag name processing functions. Accepts an
    Array
    of functions with following signature:
    javascript
    function (name){
      //do something with `name`
      return name
    }
    
    Added in 0.4.1
  • valueProcessors
    (default:
    null
    ): Allows the addition of element value processing functions. Accepts an
    Array
    of functions with following signature:
    javascript
    function (value, name){
      //do something with `name`
      return name
    }
    
    Added in 0.4.6

Options for the
Builder
class

These options are specified by

new Builder({optionName: value})
. Possible options are:
  • attrkey
    (default:
    $
    ): Prefix that is used to access the attributes. Version 0.1 default was
    @
    .
  • charkey
    (default:
    _
    ): Prefix that is used to access the character content. Version 0.1 default was
    #
    .
  • rootName
    (default
    root
    or the root key name): root element name to be used in case
    explicitRoot
    is
    false
    or to override the root element name.
  • renderOpts
    (default
    { 'pretty': true, 'indent': '  ', 'newline': '\n' }
    ): Rendering options for xmlbuilder-js.
    • pretty: prettify generated XML
    • indent: whitespace for indentation (only when pretty)
    • newline: newline char (only when pretty)
  • xmldec
    (default
    { 'version': '1.0', 'encoding': 'UTF-8', 'standalone': true }
    : XML declaration attributes.
    • xmldec.version
      A version number string, e.g. 1.0
    • xmldec.encoding
      Encoding declaration, e.g. UTF-8
    • xmldec.standalone
      standalone document declaration: true or false
  • doctype
    (default
    null
    ): optional DTD. Eg.
    {'ext': 'hello.dtd'}
  • headless
    (default:
    false
    ): omit the XML header. Added in 0.4.3.
  • allowSurrogateChars
    (default:
    false
    ): allows using characters from the Unicode surrogate blocks.
  • cdata
    (default:
    false
    ): wrap text nodes in
     instead of
    escaping when necessary. Does not add 
     if it is not required.
    Added in 0.4.5.

renderOpts
,
xmldec
,
doctype
and
headless
pass through to xmlbuilder-js.

Updating to new version

Version 0.2 changed the default parsing settings, but version 0.1.14 introduced the default settings for version 0.2, so these settings can be tried before the migration.

var xml2js = require('xml2js');
var parser = new xml2js.Parser(xml2js.defaults["0.2"]);

To get the 0.1 defaults in version 0.2 you can just use

xml2js.defaults["0.1"]
in the same place. This provides you with enough time to migrate to the saner way of parsing in
xml2js
0.2. We try to make the migration as simple and gentle as possible, but some breakage cannot be avoided.

So, what exactly did change and why? In 0.2 we changed some defaults to parse the XML in a more universal and sane way. So we disabled

normalize
and
trim
so
xml2js
does not cut out any text content. You can reenable this at will of course. A more important change is that we return the root tag in the resulting JavaScript structure via the
explicitRoot
setting, so you need to access the first element. This is useful for anybody who wants to know what the root node is and preserves more information. The last major change was to enable
explicitArray
, so everytime it is possible that one might embed more than one sub-tag into a tag, xml2js >= 0.2 returns an array even if the array just includes one element. This is useful when dealing with APIs that return variable amounts of subtags.

Running tests, development

Build Status Coverage Status Dependency Status

The development requirements are handled by npm, you just need to install them. We also have a number of unit tests, they can be run using

npm test
directly from the project root. This runs zap to discover all the tests and execute them.

If you like to contribute, keep in mind that

xml2js
is written in CoffeeScript, so don't develop on the JavaScript files that are checked into the repository for convenience reasons. Also, please write some unit test to check your behaviour and if it is some user-facing thing, add some documentation to this README, so people will know it exists. Thanks in advance!

Getting support

Please, if you have a problem with the library, first make sure you read this README. If you read this far, thanks, you're good. Then, please make sure your problem really is with

xml2js
. It is? Okay, then I'll look at it. Send me a mail and we can talk. Please don't open issues, as I don't think that is the proper forum for support problems. Some problems might as well really be bugs in
xml2js
, if so I'll let you know to open an issue instead :)

But if you know you really found a bug, feel free to open an issue instead.

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