xpath2.js - Pure JavaScript implementation of XPath 2 query language

About

xpath2.js is a DOM-agnostic open-source XPath 2.0 implementation in JavaScript. Execution engine operates using XML Schema 1.1 data types as prescribed by specification.

Features

• Full XPath 2.0 language support
• Arbitrary tree structure querying with XPath 2.0 language via custom DOMAdapter
• Custom collation support (using StaticContext)
• Custom function support (using StaticContext)
• Variable injection (using DynamicContext)

Installation

npm install xpath2.js

Usage

The simple API implementation lib/index.js provided for reference. Its primary purpose is to demonstrate implementation classes wiring and a simple usable solution.

Basic scenarious with evaluate function

xpath.evaluate(expression, evaluationContext, staticContext, initialScope, DOMAdapter)

Parameters list

Name	Type	Required	Description
expression	String	Required	xpath expression
evaluationContext	Variant	Optional	evaluation context (document, for example)
staticContext	StaticContext or Function	Optional	compilation context or namespace resolver
initialScope	Object	Optional	JavaScript variable values map
DOMAdapter	DOMAdapter	Optional	document object model adapter

Query without a context

const xpath = require("xpath2.js");
const result = xpath.evaluate("1 to 5");
console.log(result); // prints [ 1, 2, 3, 4, 5 ]

Query a document not specifying namespaces

const xpath = require("xpath2.js");
const xmldom = require("xmldom"); // You are free to use any DOM implementation
const document = new xmldom.DOMParser().parseFromString('<test>content</test>');

const result = xpath.evaluate("fn:string(/test/text())", document);
console.log(result); // prints [ 'content' ]

Query a document with namespace resolver

Evaluating expressions over documents that specify namespaces requires namespace resolver to be provided with the query. Take a note that namespace resolver is there to resolve prefixes found in XPath expressions, thus making use of prefixes in expressions scoped to the query, and not to the document.

A namespace resolver is a function that takes single argument String prefix and returns a namespace uri for it.

Exception XPST0081 will be thrown, should any of the prefixes used in expression are left unresolved.

const xpath = require("xpath2.js");
const xmldom = require("xmldom");
const document = new xmldom.DOMParser().parseFromString('<foo><a:bar xmlns:a="http://a">content</a:bar></foo>');
const namespaceResolver = function(prefix) {
    if (prefix == "b")
        return "http://a";
    return null;
};

const result = xpath.evaluate("fn:string(//b:bar/text())", document, namespaceResolver);
console.log(result); // prints [ 'content' ]

Passing a JavaScript variable to the evaluation context

const xpath = require("xpath2.js");

const result = xpath.evaluate("$a + 0.2", null, null, {a: 0.1});
console.log(result); // prints [ 0.3 ]

More challenging scenarious

Using execute function and managing contexts

const xpath = require("xpath2.js");
const xmldom = require("xmldom");
const document = new xmldom.DOMParser().parseFromString('<foo><a:bar xmlns:a="http://a">content</a:bar></foo>');
const namespaceResolver = function(prefix) {
    if (prefix == "b")
        return "http://a";
    return null;
};
const staticContext = xpath.createStaticContext(namespaceResolver);
// Set default function namespace to the one of XPath functions, so "fn" prefix can be dropped in queries
staticContext.defaultFunctionNamespace = "http://www.w3.org/2005/xpath-functions";
const dynamicContext = xpath.createDynamicContext(staticContext, document);
const expression = xpath.compile("string(//b:bar/text())", staticContext);

const result = xpath.execute(expression, dynamicContext);
console.log(result); // prints [ 'content' ]

Note! Dynamic context carries date/time obtained during its creation