Create XML attribute using XPath

Question

I want to create an xml attribute but in order to find the element I want to add the query on, I need to use xpath. How can I do this?

Example =

const xmlText = `<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<book>
  <title lang="eng">Harry Potter</title>
  <price>29.99</price>
</book>
<book>
  <title id="somethingeng">Learning XML</title>
  <price>39.95</price>
</book>
</bookstore>`;

var doc = new DOMParser().parseFromString(xmlText,'text/xml');

var r = doc.evaluate("//*[@lang[contains(.,'eng')]]", doc, null, XPathResult.ANY_TYPE, null);

I want to create an attribute for this r;

Answer 1

First of all the xmlText string should be a template literals now that is has new lines.

evaluate() seamed fine, but the result of that is a XPathResult that needs to be iterated with XPathResult.iterateNext() .

 const xmlText = `<?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book> <title lang="eng">Harry Potter</title> <price>29.99</price> </book> <book> <title id="somethingeng">Learning XML</title> <price>39.95</price> </book> </bookstore>`; var doc = new DOMParser().parseFromString(xmlText,'text/xml'); var r = doc.evaluate("//*[@lang[contains(.,'eng')]]", doc, null, XPathResult.ANY_TYPE, null); var next = r.iterateNext(); while (next) { console.log(next.textContent); next = r.iterateNext(); }

Update

Based on the iterator you need to collect the nodes that you are interested in and then alter them afterwards. In the following I created functions that can create child elements and attributes based on a XPath expression and an object representing the new data.

 const xmlText = `<?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book> <title lang="eng">Harry Potter</title> <price>29.99</price> </book> <book> <title id="somethingeng">Learning XML</title> <price>39.95</price> </book> </bookstore>`; var doc = new DOMParser().parseFromString(xmlText, 'text/xml'); function addAttribute(doc, xpath, obj) { let r = doc.evaluate(xpath, doc, null, XPathResult.ANY_TYPE, null); let nodes = []; let next = r.iterateNext(); while (next) { nodes.push(next); next = r.iterateNext(); } nodes.forEach(node => { Object.keys(obj).forEach(key => { let newattr = doc.createAttribute(key); newattr.value = obj[key]; node.setAttributeNode(newattr); }); }); } function addChildNode(doc, xpath, obj) { let r = doc.evaluate(xpath, doc, null, XPathResult.ANY_TYPE, null); let nodes = []; let next = r.iterateNext(); while (next) { console.log(next.textContent); nodes.push(next); next = r.iterateNext(); } nodes.forEach(node => { Object.keys(obj).forEach(key => { let newnode = doc.createElement(key); newnode.textContent = obj[key]; node.appendChild(newnode); }); }); } addAttribute(doc, "//title[@lang[contains(.,'eng')]]", {"data-lang":"eng", index: 2}); addChildNode(doc, "//book[number(price) < 30]", {sale: true}); console.log(doc.documentElement.outerHTML);

Answer 2

Found the solution by using XPathResult.snapshotItem() .

 var xmlText = `<?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book> <title lang="eng">Harry Potter</title> <price>29.99</price> </book> <book> <title id=\"somethingeng\">Learning XML</title> <price>39.95</price> </book> </bookstore>`; var doc = new DOMParser().parseFromString(xmlText, 'text/xml'); var r = doc.evaluate("//*[@id[contains(.,'eng')]]", doc, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null); var index = 0; while (index < r.snapshotLength) { var next = r.snapshotItem(index); next.setAttribute("value", "val"); index++; } var xmlSerializer = new XMLSerializer(); const updatedDoc = xmlSerializer.serializeToString(doc); console.log(updatedDoc);