How to set default value for missing elements in XML using XPath?

user_3045568 0
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This is my XML

<?xml version="1.0" encoding="UTF-8"?>
<message>
    <return>
        <BYTES_LENGTH>12019</BYTES_LENGTH>
        <STATUS>DONE</STATUS>
    </return>
    <return>
        <BYTES_LENGTH>1129</BYTES_LENGTH>
        <STATUS>DONE</STATUS>
        <ERROR_CODE>NO MESSAGE FOUND</ERROR_CODE>
    </return>
</message>

I am writing a logic in Node JS using xml2js-xpath library to extract ERROR_CODES and STATUS values in array using the following code -

var xml2js = require("xml2js")

const parserXml = new xml2js.Parser();
var val = [];
parserXml.parseString(data, (err, result) => {
STATUS = xpath.find(result, '//STATUS');
ERRORS = xpath.find(result, '//ERROR_CODE');
val.push(STATUS);
val.push(ERRORS);
}

Expected Result:

[  [ 'DONE', 'DONE' ],  [ '', 'NO MESSAGE FOUND' ]  ]

But I am getting this instead

[  [ 'DONE', 'DONE' ],  [ 'NO MESSAGE FOUND' ]  ]

How can I fix this to include blank value if the element doesn't exist in the XML node. Should I used a different library? What is the best way to handle this?

node.js xpath xml javascript
1 Answers

With XPath 3.1 (e.g. SaxonJS) you could use the XPath

array { 
  array { /message/return/string(STATUS) }, 
  array { /message/return/string(ERROR_CODE) } 
}

e.g.

const SaxonJS = require("saxon-js");

const xml = `<?xml version="1.0" encoding="UTF-8"?>
<message>
    <return>
        <BYTES_LENGTH>12019</BYTES_LENGTH>
        <STATUS>DONE</STATUS>
    </return>
    <return>
        <BYTES_LENGTH>1129</BYTES_LENGTH>
        <STATUS>DONE</STATUS>
        <ERROR_CODE>NO MESSAGE FOUND</ERROR_CODE>
    </return>
</message>`;

const result = SaxonJS.XPath.evaluate(`parse-xml(.) ! array { 
  array { /message/return/string(STATUS) }, 
  array { /message/return/string(ERROR_CODE) } 
}`, xml);

console.log(result);
user_2522280
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