解析XML文件是开发中常见的需求之一。为了以一种简单易用的方式访问XML数据，你可能不想编译一个C解析器，而是想寻找一个更方便的解决方案。那么，xml2js就是你需要的工具！xml2js是一个简单的XML到JavaScript对象转换器，支持双向转换。它使用了sax-js和xmlbuilder-js这两个工具库。
安装
最简单的安装xml2js的方式是使用npm。只需执行npm install xml2js，npm将会下载xml2js及其所有依赖。xml2js也可以通过Bower进行安装，只需执行bower install xml2js，Bower将会下载xml2js及其所有依赖。
用法
由于你是一位非常聪明的开发者，所以不需要过多的教程指导。解析XML应该是一件简单的事情，我们直接通过一些示例进行学习。
简短用法
你希望尽可能简单、轻松地解析XML吗？使用以下代码：
var parseString = require('xml2js').parseString;
var xml = "<root>Hello xml2js!</root>"
parseString(xml, function (err, result) {
console.dir(result);
});这真是再简单不过了，对吧？这个方法适用于xml2js的0.2.3版本及以上。使用CoffeeScript时，代码如下：
CoffeeScript 可能比较小众，但是官方文档有举例了相关内容，故本文进行保留。
{parseString} = require 'xml2js'
xml = "<root>Hello xml2js!</root>"
parseString xml, (err, result) ->
console.dir result如果你需要一些特殊的选项，也不用担心，xml2js支持许多选项（见下文），你可以将这些选项作为第二个参数进行指定：
parseString(xml, {trim: true}, function (err, result) {
});实例方法
如果你之前一直使用xml-simple或者自己封装的方法来处理XML，那么从0.1.11版本开始，xml2js为你添加了以下方法：
xml
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');
});
});" aria-label="复制" data-bs-original-title="复制">
<i class="far fa-copy"></i>
</button>
</div>
</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">var</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'fs'</span>),
xml2js = <span class="hljs-built_in">require</span>(<span class="hljs-string">'xml2js'</span>);
<span class="hljs-keyword">var</span> parser = <span class="hljs-keyword">new</span> xml2js.<span class="hljs-title class_">Parser</span>();
fs.<span class="hljs-title function_">readFile</span>(__dirname + <span class="hljs-string">'/foo.xml'</span>, <span class="hljs-keyword">function</span>(<span class="hljs-params">err, data</span>) {
parser.<span class="hljs-title function_">parseString</span>(data, <span class="hljs-keyword">function</span> (<span class="hljs-params">err, result</span>) {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">dir</span>(result);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Done'</span>);
});
});</pre><p>看吧，没有事件监听器！</p><p>你还可以使用<a target="_blank" href="https://link.segmentfault.com/?enc=64CJgkgNv%2FHcqakFhQdNRw%3D%3D.pdeyja27cdJxnadxlJiRGBEqxQCXIlkWqjF5l8wAOFzcQAOxS3nXWpEHHBFmePi1">CoffeeScript</a>来进一步减少代码的冗余：</p><div class="widget-codetool" style="display: none;">
<div class="widget-codetool--inner">
<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="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.'" aria-label="复制" data-bs-original-title="复制">
<i class="far fa-copy"></i>
</button>
</div>
</div><pre class="coffeescript hljs language-coffeescript">fs = <span class="hljs-built_in">require</span> <span class="hljs-string">'fs'</span>,
xml2js = <span class="hljs-built_in">require</span> <span class="hljs-string">'xml2js'</span>
parser = <span class="hljs-keyword">new</span> xml2js.Parser()
fs.readFile __dirname + <span class="hljs-string">'/foo.xml'</span>, <span class="hljs-function"><span class="hljs-params">(err, data)</span> -></span>
parser.parseString data, <span class="hljs-function"><span class="hljs-params">(err, result)</span> -></span>
console.dir result
console.log <span class="hljs-string">'Done.'</span></pre><p>但是，如果你忘记使用<code>new</code>关键字创建一个新的<code>Parser</code>对象会怎么样？从0.2.8开始，你也可以不使用这个关键字。从0.2.8开始，你可以不使用它，在这种情况下，xml2js会帮助你添加它，以保证不会再出现意外和莫名其妙的bug!</p><h3 id="item-2-3">Promise 用法</h3><div class="widget-codetool" style="display: none;">
<div class="widget-codetool--inner">
<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="var xml2js = require('xml2js');
var xml = '<foo></foo>';
// 1. With parser
var parser = new xml2js.Parser(/* options */);
parser.parseStringPromise(xml).then(function (result) {
console.dir(result);
console.log('Done');
})
.catch(function (err) {
// Failed
});
// 2. Without parser
xml2js.parseStringPromise(xml /*, options */).then(function (result) {
console.dir(result);
console.log('Done');
})
.catch(function (err) {
// Failed
});" aria-label="复制" data-bs-original-title="复制">
<i class="far fa-copy"></i>
</button>
</div>var xml2js = require('xml2js');
var xml = '<foo></foo>';
// 1. With parser
var parser = new xml2js.Parser(/* options */);
parser.parseStringPromise(xml).then(function (result) {
console.dir(result);
console.log('Done');
})
.catch(function (err) {
// Failed
});
`` ``<span class="hljs-comment">``// 2. Without parser``</span>``
xml2js.``<span class="hljs-title function_">``parseStringPromise``</span>``(xml ``<span class="hljs-comment">``/*, options */``</span>``).``<span class="hljs-title function_">``then``</span>``(``<span class="hljs-keyword">``function``</span>`` (``<span class="hljs-params">``result``</span>``) {
``<span class="hljs-variable language_">``console``</span>``.``<span class="hljs-title function_">``dir``</span>``(result);
``<span class="hljs-variable language_">``console``</span>``.``<span class="hljs-title function_">``log``</span>``(``<span class="hljs-string">``'Done'``</span>``);
})
.``<span class="hljs-title function_">``catch``</span>``(``<span class="hljs-keyword">``function``</span>`` (``<span class="hljs-params">``err``</span>``) {
``<span class="hljs-comment">``// Failed``</span>``
});``</pre><ol><li>``使用解析器进行解析：通过创建xml2js解析器的实例，调用解析器的``<code>``parseStringPromise``</code>``方法对XML数据进行解析，并通过``<code>``.then()``</code>``方法处理解析成功的结果，通过``<code>``.catch()``</code>``方法处理解析过程中的错误。``</li><li>``不使用解析器直接解析：直接调用xml2js库的``<code>``parseStringPromise``</code>``方法对XML数据进行解析，通过``<code>``.then()``</code>``方法处理解析成功的结果，通过``<code>``.catch()``</code>``方法处理解析过程中的错误。这种方法省去了创建解析器实例的步骤，直接调用库函数进行解析。``</li></ol><h2 id="item-3">``使用 XML 构建器``</h2><p>``自 0.4.0 版本起，xml2js 还支持使用对象来构建 XML。下面是一个示例：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="const xml2js = require('xml2js');
const obj = {name: "Super", Surname: "Man", age: 23};
const builder = new xml2js.Builder();
const xml = builder.buildObject(obj);" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">``const``</span>`` xml2js = ``<span class="hljs-built_in">``require``</span>``(``<span class="hljs-string">``'xml2js'``</span>``);
``<span class="hljs-keyword">``const``</span>`` obj = {``<span class="hljs-attr">``name``</span>``: ``<span class="hljs-string">``"Super"``</span>``, ``<span class="hljs-title class_">``Surname``</span>``: ``<span class="hljs-string">``"Man"``</span>``, ``<span class="hljs-attr">``age``</span>``: ``<span class="hljs-number">``23``</span>``};
``<span class="hljs-keyword">``const``</span>`` builder = ``<span class="hljs-keyword">``new``</span>`` xml2js.``<span class="hljs-title class_">``Builder``</span>``();
``<span class="hljs-keyword">``const``</span>`` xml = builder.``<span class="hljs-title function_">``buildObject``</span>``(obj);``</pre><p>``上述代码将生成如下的 XML：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
<name>Super</name>
<Surname>Man</Surname>
<age>23</age>
</root>" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="xml hljs language-xml"><span class="hljs-meta"><``?xml version=``<span class="hljs-string">``"1.0"``</span>`` encoding=``<span class="hljs-string">``"UTF-8"``</span>`` standalone=``<span class="hljs-string">``"yes"``</span>``?``></span>``
``<span class="hljs-tag"><<span class="hljs-name">``root``</span>></span>``
``<span class="hljs-tag"><<span class="hljs-name">``name``</span>></span>``Super``<span class="hljs-tag"><``/``<span class="hljs-name">``name``</span>></span>``
``<span class="hljs-tag"><<span class="hljs-name">``Surname``</span>></span>``Man``<span class="hljs-tag"><``/``<span class="hljs-name">``Surname``</span>></span>``
``<span class="hljs-tag"><<span class="hljs-name">``age``</span>></span>``23``<span class="hljs-tag"><``/``<span class="hljs-name">``age``</span>></span>``
``<span class="hljs-tag"><``/``<span class="hljs-name">``root``</span>></span></pre><p>``通过设置 ``<code>``cdata``</code>`` 选项为 ``<code>``true``</code>``，可以支持写入 CDATA。``</p><h3 id="item-3-4">``指定属性``</h3><p>``使用 xml2js，你可以指定 XML 元素的属性。下面是一个示例：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="const xml2js = require('xml2js');
const obj = {root: {$: {id: "my id"}, _: "my inner text"}};
const builder = new xml2js.Builder();
const xml = builder.buildObject(obj);" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">``const``</span>`` xml2js = ``<span class="hljs-built_in">``require``</span>``(``<span class="hljs-string">``'xml2js'``</span>``);
``<span class="hljs-keyword">``const``</span>`` obj = {``<span class="hljs-attr">``root``</span>``: {``<span class="hljs-attr">``$``</span>``: {``<span class="hljs-attr">``id``</span>``: ``<span class="hljs-string">``"my id"``</span>``}, ``<span class="hljs-attr">``_``</span>``: ``<span class="hljs-string">``"my inner text"``</span>``}};
``<span class="hljs-keyword">``const``</span>`` builder = ``<span class="hljs-keyword">``new``</span>`` xml2js.``<span class="hljs-title class_">``Builder``</span>``();
``<span class="hljs-keyword">``const``</span>`` xml = builder.``<span class="hljs-title function_">``buildObject``</span>``(obj);``</pre><p>``上述代码将生成如下的 XML：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root id="my id">my inner text</root>" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="xml hljs language-xml"><span class="hljs-meta"><``?xml version=``<span class="hljs-string">``"1.0"``</span>`` encoding=``<span class="hljs-string">``"UTF-8"``</span>`` standalone=``<span class="hljs-string">``"yes"``</span>``?``></span>``
``<span class="hljs-tag"><<span class="hljs-name">``root``</span>`` ``<span class="hljs-attr">``id``</span>``=``<span class="hljs-string">``"my id"``</span>></span>``my inner text``<span class="hljs-tag"><``/``<span class="hljs-name">``root``</span>></span></pre><h3 id="item-3-5">``添加 xmlns 属性``</h3><p>``xml2js 还支持在生成的 XML 中添加 XML 命名空间前缀和 URI 对，通过使用 ``<code>``xmlns``</code>`` 属性。``</p><p>``在根元素上声明默认命名空间的示例：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="const obj = {
Foo: {
$: {
"xmlns": "http://foo.com"
}
}
};" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">``const``</span>`` obj = {
``<span class="hljs-title class_">``Foo``</span>``: {
``<span class="hljs-attr">``$``</span>``: {
``<span class="hljs-string">``"xmlns"``</span>``: ``<span class="hljs-string">``"http://foo.com"``</span>``
}
}
};``</pre><p>``通过调用 ``<code>``buildObject(obj)``</code>`` 方法，将生成以下 XML：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="<Foo xmlns="http://foo.com"/>" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="xml hljs language-xml"><span class="hljs-tag"><<span class="hljs-name">``Foo``</span>`` ``<span class="hljs-attr">``xmlns``</span>``=``<span class="hljs-string">``"http://foo.com"``</span>``/``></span></pre><p>``在非根元素上声明非默认命名空间的示例：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="const obj = {
'foo:Foo': {
$: {
'xmlns:foo': 'http://foo.com'
},
'bar:Bar': {
$: {
'xmlns:bar': 'http://bar.com'
}
}
}
};" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">``const``</span>`` obj = {
``<span class="hljs-string">``'foo:Foo'``</span>``: {
``<span class="hljs-attr">``$``</span>``: {
``<span class="hljs-string">``'xmlns:foo'``</span>``: ``<span class="hljs-string">``'http://foo.com'``</span>``
},
``<span class="hljs-string">``'bar:Bar'``</span>``: {
``<span class="hljs-attr">``$``</span>``: {
``<span class="hljs-string">``'xmlns:bar'``</span>``: ``<span class="hljs-string">``'http://bar.com'``</span>``
}
}
}
};``</pre><p>``通过调用 ``<code>``buildObject(obj)``</code>`` 方法，将生成以下 XML：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="<foo:Foo xmlns:foo="http://foo.com">
<bar:Bar xmlns:bar="http://bar.com"/>
</foo:Foo>" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="xml hljs language-xml"><span class="hljs-tag"><<span class="hljs-name">``foo:Foo``</span>`` ``<span class="hljs-attr">``xmlns:foo``</span>``=``<span class="hljs-string">``"http://foo.com"``</span>></span>``
``<span class="hljs-tag"><<span class="hljs-name">``bar:Bar``</span>`` ``<span class="hljs-attr">``xmlns:bar``</span>``=``<span class="hljs-string">``"http://bar.com"``</span>``/``></span>``
``<span class="hljs-tag"><``/``<span class="hljs-name">``foo:Foo``</span>></span></pre><h3 id="item-3-6">``处理属性、标签名和值``</h3><p>``自 0.4.1 版本起，你可以选择提供解析器的属性名和标签名处理器，以及元素值处理器（自 0.4.14 版本起，还可以提供属性值处理器）。``</p><p>``下面是一个示例，演示如何将属性名和标签名转换为大写：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="function nameToUpperCase(name) {
return name.toUpperCase();
}
// 将所有属性和标签名及其值转换为大写
parseString(xml, {
tagNameProcessors: [nameToUpperCase],
attrNameProcessors: [nameToUpperCase],
valueProcessors: [nameToUpperCase],
attrValueProcessors: [nameToUpperCase]
}, function (err, result) {
// 处理后的数据
});" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">``function``</span>`` ``<span class="hljs-title function_">``nameToUpperCase``</span>``(``<span class="hljs-params">``name``</span>``) {
``<span class="hljs-keyword">``return``</span>`` name.``<span class="hljs-title function_">``toUpperCase``</span>``();
}
``<span class="hljs-comment">``// 将所有属性和标签名及其值转换为大写``</span>``
``<span class="hljs-title function_">``parseString``</span>``(xml, {
``<span class="hljs-attr">``tagNameProcessors``</span>``: [nameToUpperCase],
``<span class="hljs-attr">``attrNameProcessors``</span>``: [nameToUpperCase],
``<span class="hljs-attr">``valueProcessors``</span>``: [nameToUpperCase],
``<span class="hljs-attr">``attrValueProcessors``</span>``: [nameToUpperCase]
}, ``<span class="hljs-keyword">``function``</span>`` (``<span class="hljs-params">``err, result``</span>``) {
``<span class="hljs-comment">``// 处理后的数据``</span>``
});``</pre><p><code>``tagNameProcessors``</code>`` 和 ``<code>``attrNameProcessors``</code>`` 选项接受一个函数数组，函数的签名如下：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="function (name) {
// 对 `name` 做一些处理
return name;
}" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">``function``</span>`` (``<span class="hljs-params">``name``</span>``) {
``<span class="hljs-comment">``// 对 `name` 做一些处理``</span>``
``<span class="hljs-keyword">``return``</span>`` name;
}``</pre><p><code>``attrValueProcessors``</code>`` 和 ``<code>``valueProcessors``</code>`` 选项接受一个函数数组，函数的签名如下：``</p><div class="widget-codetool" style="display: none;">``
``<div class="widget-codetool--inner">``
``<button type="button" class="btn btn-dark rounded-0 sflex-center copyCode" data-toggle="tooltip" data-placement="top" data-clipboard-text="function (value, name) {
// `name` 将是节点名或属性名
// 对 `value` 做一些处理，可以根据节点或属性名自定义处理方式
return value;
}" aria-label="复制" data-bs-original-title="复制">``
``<i class="far fa-copy"></i>``
``</button>``
``</div>``
``</div><pre class="javascript hljs language-javascript"><span class="hljs-keyword">``function``</span>`` (``<span class="hljs-params">``value, name``</span>``) {
``<span class="hljs-comment">``// `name` 将是节点名或属性名``</span>``
``<span class="hljs-comment">``// 对 `value` 做一些处理，可以根据节点或属性名自定义处理方式``</span>``
``<span class="hljs-keyword">``return``</span>`` value;
}``</pre><p>``xml2js 提供了一些内置的处理器，可以在 ``<code>``lib/processors.js``</code>`` 文件中找到：``</p><ul><li><code>``normalize``</code>``：将名称转换为小写（当 ``<code>``options.normalize``</code>`` 设置为 ``<code>``true``</code>`` 时自动使用）``</li><li><code>``firstCharLowerCase``</code>``：将首字母转换为小写。例如，'MyTagName' 变为 'myTagName'``</li><li><code>``stripPrefix``</code>``：去除 XML 命名空间前缀。例如，``<code><``foo:Bar/``></code>`` 将变为 'Bar'（注意：xmlns 前缀不会被去除）``</li><li><code>``parseNumbers``</code>``：将类似整数的字符串解析为整数，将类似浮点数的字符串解析为浮点数。例如，"0" 变为 0，"15.56" 变为 15.56``</li><li><code>``parseBooleans``</code>``：将类似布尔值的字符串解析为布尔值。例如，"true" 变为 true，"false" 变为 false``</li></ul><p>``xml2js 提供了强大的功能，使得在 Node.js 应用程序中解析和构建 XML 变得简单而灵活。无论你是需要解析复杂的 XML 文档，还是需要构建自定义的 XML 输出，xml2js 都是一个值得尝试的工具。``</p><p>``参考文档：``<a target="_blank" href="https://link.segmentfault.com/?enc=etR%2BztW16kPCxB2NU7oIPQ%3D%3D.Cwbulk4XaYVwVQl7fU3ltbURkK1TcyTIHwRRPM8izEKbuj9UTgoUJhTI2v3riukOtnvQ3QQ0bk1sK%2F%2FiZ7u%2BDg%3D%3D">``Leonidas-from-XIV/node-xml2js: XML to JavaScript object converter.``</a></p>``
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