xml2js

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. Uses sax-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.

Usage

This will have to do, unless you're looking for some fancy extensive documentation. If you're looking for every single option and usage, see the unit tests.

Simple as pie usage

The simplest way to use it, is to use the optional callback interface added in 0.1.11. That's right, if you have been using xml-simple or a home-grown wrapper, this is 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! Alternatively you can still use the traditional addListener variant:

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

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

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.'

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).

Options

Apart from the default settings, there is a number of options that can be specified for the parser. Options are specified by new Parser({optionName: value}). Possible options are:

• attrkey (default: $): Prefix that is used to access the attributes. Version 0.1 default was @.
• charkey (default: _): Prefix that is used to access the character content. Version 0.1 default was #.
• explicitCharkey (default: false)
• trim (default: false): Trim the whitespace at the beginning and end of text nodes.
• normalizeTags (default: false): Normalize all tag names to lowercase.
• normalize (default: false): Trim whitespaces inside text nodes.
• explicitRoot (default: true): Set this if you want to get the root node in the resulting object.
• emptyTag (default: undefined): what will the value of empty nodes be. Default is {}.
• explicitArray (default: true): Always put child nodes in an array if true; otherwise an array is created only if there is more than one.
• ignoreAttrs (default: false): Ignore all XML attributes and only create text nodes.
• mergeAttrs (default: false): Merge attributes and child elements as properties of the parent, instead of keying attributes off a child attribute object. This option is ignored if ignoreAttrs is false.
• validator (default null): You can specify a callable that validates the resulting structure somehow, however you want. See unit tests for an example.
• xmlns (default false): Give each element a field usually called '$ns' (the first character is the same as attrkey) that contains its local name and namespace URI.

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

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 zap directly from the project root.