xpath

What is xpath?

The xpath npm package is a Node.js module that allows users to query XML documents using XPath expressions. It provides a way to navigate and select nodes in an XML document tree, extract information, and manipulate the content.

What are xpath's main functionalities?

Evaluating XPath expressions

This feature allows you to evaluate XPath expressions against an XML document and returns the matching nodes.

const xpath = require('xpath'),
     dom = require('xmldom').DOMParser;
let doc = new dom().parseFromString('<book><title>Harry Potter</title></book>');
let nodes = xpath.select('//title', doc);
console.log(nodes[0].textContent); // Harry Potter

Registering custom namespaces

This feature enables the use of custom namespaces when evaluating XPath expressions, which is necessary when querying XML documents that include namespaces.

const select = xpath.useNamespaces({
  'x': 'http://www.w3.org/1999/xhtml'
});
let nodes = select('//x:div', doc);

Using XPath functions

This feature allows the use of XPath functions within the expression to perform operations like counting nodes, string manipulation, etc.

let result = xpath.select('count(//title)', doc);
console.log(result); // 1

Other packages similar to xpath

cheerio

Cheerio is a fast, flexible, and lean implementation of core jQuery designed specifically for the server. It allows for manipulation of the DOM using a familiar jQuery-like API. Cheerio parses markup and provides an API for traversing/manipulating the resulting data structure; it does not interpret XPath but uses CSS selectors instead.

jsdom

jsdom is a pure-JavaScript implementation of many web standards, notably the WHATWG DOM and HTML Standards, for use with Node.js. It is more of a complete browser environment simulator that can also execute scripts, unlike xpath which is focused solely on XPath queries.

xml2js

xml2js is a simple XML to JavaScript object converter. It supports bi-directional conversion. Unlike xpath, which is used for querying XML documents, xml2js is used for parsing XML into JavaScript objects and vice versa.

README

xpath

DOM 3 XPath 1.0 implemention and helper for JavaScript, with node.js support.

Originally written by Cameron McCormack (blog).

Additional contributions from
Yaron Naveh (blog)
goto100
Thomas Weinert
Jimmy Rishe
and others

Install

Install with npm:

npm install xpath

xpath is xml engine agnostic but I recommend to use xmldom:

npm install xmldom

API Documentation

Can be found here. See below for example usage.

Your first xpath:

var xpath = require('xpath')
  , dom = require('xmldom').DOMParser

var xml = "<book><title>Harry Potter</title></book>"
var doc = new dom().parseFromString(xml)
var nodes = xpath.select("//title", doc)

console.log(nodes[0].localName + ": " + nodes[0].firstChild.data)
console.log("Node: " + nodes[0].toString())

➡

title: Harry Potter
Node: <title>Harry Potter</title>

Alternatively

Using the same interface you have on modern browsers (MDN)

var node = null;
var xml = "<book author='J. K. Rowling'><title>Harry Potter</title></book>"
var doc = new dom().parseFromString(xml)
var result = xpath.evaluate(
    "/book/title",            // xpathExpression
    doc,                        // contextNode
    null,                       // namespaceResolver
    xpath.XPathResult.ANY_TYPE, // resultType
    null                        // result
)

node = result.iterateNext();
while (node) {
    console.log(node.localName + ": " + node.firstChild.data);
    console.log("Node: " + node.toString());

    node = result.iterateNext();
}

➡

title: Harry Potter
Node: <title>Harry Potter</title>

Evaluate string values directly:

var xml = "<book><title>Harry Potter</title></book>";
var doc = new dom().parseFromString(xml);
var title = xpath.select("string(//title)", doc);

console.log(title);

➡

Harry Potter

Namespaces

var xml = "<book><title xmlns='myns'>Harry Potter</title></book>"
var doc = new dom().parseFromString(xml)
var node = xpath.select("//*[local-name(.)='title' and namespace-uri(.)='myns']", doc)[0]

console.log(node.namespaceURI)

➡

myns

Namespaces with easy mappings

var xml = "<book xmlns:bookml='http://example.com/book'><bookml:title>Harry Potter</bookml:title></book>"
var select = xpath.useNamespaces({"bookml": "http://example.com/book"});

console.log(select('//bookml:title/text()', doc)[0].nodeValue);

➡

Harry Potter

Default namespace with mapping

var xml = "<book xmlns='http://example.com/book'><title>Harry Potter</title></book>"
var select = xpath.useNamespaces({"bookml": "http://example.com/book"});

console.log(select('//bookml:title/text()', doc)[0].nodeValue);

➡

Harry Potter

Attributes

var xml = "<book author='J. K. Rowling'><title>Harry Potter</title></book>"
var doc = new dom().parseFromString(xml)
var author = xpath.select1("/book/@author", doc).value

console.log(author)

➡

J. K. Rowling

License

MIT