How nodejs processes xml

Node.js is a platform for server-side programming using JavaScript. Many times we need to process XML data to complete some tasks. This article explains how to process XML data in Node.js.

What is XML?

XML is also called extensible markup language. It is a markup language that defines rules to describe the structure and content of a document. Unlike HTML, XML does not predefine any elements. This means we can create our own tags and use them to describe the data.

The general format of XML is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <person>
        <name>John</name>
        <age>30</age>
    </person>
    <person>
        <name>Jane</name>
        <age>25</age>
    </person>
</root>

How to process XML data in Node.js?

In Node.js, we can use the built-in module fs to read and write XML files. But for parsing and serializing XML data, we need to use third-party modules.

Parsing XML data

In Node.js, we can use the xml2js module to easily parse XML data. xml2js Provides a way to convert XML data into JavaScript objects.

We can install the module first:

npm install xml2js

In the code of our application, we can use the module like this:

const xml2js = require('xml2js');

const xml = `
<?xml version="1.0" encoding="UTF-8"?>
<root>
    <person>
        <name>John</name>
        <age>30</age>
    </person>
    <person>
        <name>Jane</name>
        <age>25</age>
    </person>
</root>
`;

const parser = new xml2js.Parser({ explicitArray: false });
parser.parseString(xml, (err, result) => {
    if (err) {
        console.error(err);
    } else {
        console.log(result);
    }
});

In the above code, we first Defines a string containing XML data. We then create an instance of the xml2js parser and use the parseString method to parse the XML data into a JavaScript object. explicitArray The attribute is to ensure that the returned result must be an object, not an array.

If we run the above code, we will get the following output:

{
    root: {
        person: [
            {
                name: 'John',
                age: '30'
            },
            {
                name: 'Jane',
                age: '25'
            }
        ]
    }
}

From the output, we can see that the parser has successfully converted the XML data into a nested JavaScript object.

Serializing JavaScript objects to XML

After processing JavaScript objects, in some cases we need to serialize JavaScript objects into XML data. We can use the Builder class provided in the xml2js module to achieve this.

We can install the module first:

npm install xml2js

In the code of our application, we can use it like this:

const xml2js = require('xml2js');

const data = {
    root: {
        person: [
            {
                name: 'John',
                age: '30'
            },
            {
                name: 'Jane',
                age: '25'
            }
        ]
    }
};

const builder = new xml2js.Builder();
const xml = builder.buildObject(data);
console.log(xml);

In the above code, we first define a JavaScript objects to store data. We then create a Builder instance of xml2js and use its buildObject() method to serialize our JavaScript object into XML data.

When we run the above code, we will get the following output:

<root>
    <person>
        <name>John</name>
        <age>30</age>
    </person>
    <person>
        <name>Jane</name>
        <age>25</age>
    </person>
</root>

As you can see from the output, we have successfully serialized the JavaScript object into an XML data.

Conclusion

Now, we know how to process XML data in Node.js. Whether you are reading data from XML files, converting JSON to XML or converting XML data to JSON, the xml2js library is a very convenient and useful library. It helps us process and manipulate XML data more easily.

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