namespace-lookup

Find the longest prefix that a string starts with

This Node package implements a radix tree too efficiently look up whether a string starts with a prefix from a set of prefix strings.

Table of Contents

• Install
• Usage
• Maintainers
• License

Install

npm install namespace-lookup

Usage

import { Namespaces } from "namespace-lookup"

const namespaces = new Namespaces() // optionally pass an array of prefixes

namespaces.add("http://purl.org/dc/elements/1.1/")
namespaces.add("http://purl.org/dc/terms/")

namespaces.lookup("http://purl.org/dc/terms/title") // http://purl.org/dc/terms/
namespaces.lookup("http://schema.org/title")        // undefined

An alternative, less performant implementation is this (also exportable):

class NamespacesArray extends Set {
  lookup(str) {
    for (let namespace of [...this].sort((x,y) => y.length - x.length)) {
      if (str.startsWith(namespace)) {
        return namespace
      }
    }
  }
}

Class Namespaces also supports to add prefixes with a payload (any value except null) to be returned instead:

namespaces.add("http://purl.org/dc/elements/1.1/","dc")
namespaces.add("http://purl.org/dc/terms/","dct")

namespaces.lookup("http://purl.org/dc/terms/title") // dct

Prefixes and payloads can also be passed as object:

namespaces = new Namespaces({
  "http://purl.org/dc/elements/1.1/": "dc",
  "http://purl.org/dc/terms/": "dct"
})

Method tree returns a clean copy of the radix tree for debugging and vizualization.

const tree = namespaces.tree()
console.log(JSON.stringify(tree,0,2))

Maintainers

• @nichtich (Jakob Voß)

Contribute

Contributions are welcome! Best use the issue tracker for questions, bug reports, and/or feature requests!

License

The implementation is based on a detailed description of the algorithm by Matt Roseman.

MIT license