@hmb-research/x-ray

v3.1.0

Published

2 months ago

structure any website

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tsopic

api cheerio scrape scraper structure web crawler spider webscraping data-extraction html-parser

x-ray

var Xray = require('@hmb-research/x-ray')
var x = Xray()

x('https://blog.ycombinator.com/', '.post', [
  {
    title: 'h1 a',
    link: '.article-title@href'
  }
])
  .paginate('.nav-previous a@href')
  .limit(3)
  .write('results.json')

Installation

npm install @hmb-research/x-ray

Features

Flexible schema: Supports strings, arrays, arrays of objects, and nested object structures. The schema is not tied to the structure of the page you're scraping, allowing you to pull the data in the structure of your choosing.
Composable: The API is entirely composable, giving you great flexibility in how you scrape each page.
Pagination support: Paginate through websites, scraping each page. X-ray also supports a request delay and a pagination limit. Scraped pages can be streamed to a file, so if there's an error on one page, you won't lose what you've already scraped.
Crawler support: Start on one page and move to the next easily. The flow is predictable, following a breadth-first crawl through each of the pages.
Responsible: X-ray has support for concurrency, throttles, delays, timeouts and limits to help you scrape any page responsibly.
Pluggable drivers: Swap in different scrapers depending on your needs. Currently supports HTTP and PhantomJS driver drivers. In the future, I'd like to see a Tor driver for requesting pages through the Tor network.

Selector API

xray(url, selector)(fn)

Scrape the url for the following selector, returning an object in the callback fn. The selector takes an enhanced jQuery-like string that is also able to select on attributes. The syntax for selecting on attributes is selector@attribute. If you do not supply an attribute, the default is selecting the innerText.

Here are a few examples:

Scrape a single tag

xray('http://google.com', 'title')(function(err, title) {
  console.log(title) // Google
})

Scrape a single class

xray('http://reddit.com', '.content')(fn)

Scrape an attribute

xray('http://techcrunch.com', 'img.logo@src')(fn)

Scrape innerHTML

xray('http://news.ycombinator.com', 'body@html')(fn)

xray(url, scope, selector)

You can also supply a scope to each selector. In jQuery, this would look something like this: $(scope).find(selector).

xray(html, scope, selector)

Instead of a url, you can also supply raw HTML and all the same semantics apply.

var html = '<body><h2>Pear</h2></body>'
x(html, 'body', 'h2')(function(err, header) {
  header // => Pear
})

API

xray.driver(driver)

Specify a driver to make requests through. Available drivers include:

request - A simple driver built around request. Use this to set headers, cookies or http methods.
phantom - A high-level browser automation library. Use this to render pages or when elements need to be interacted with, or when elements are created dynamically using javascript (e.g.: Ajax-calls).

xray.stream()

Returns Readable Stream of the data. This makes it easy to build APIs around x-ray. Here's an example with Express:

var app = require('express')()
var x = require('x-ray')()

app.get('/', function(req, res) {
  var stream = x('http://google.com', 'title').stream()
  stream.pipe(res)
})

xray.write([path])

Stream the results to a path.

If no path is provided, then the behavior is the same as .stream().

xray.then(cb)

Constructs a Promise object and invoke its then function with a callback cb. Be sure to invoke then() at the last step of xray method chaining, since the other methods are not promisified.

x('https://dribbble.com', 'li.group', [
  {
    title: '.dribbble-img strong',
    image: '.dribbble-img [data-src]@data-src'
  }
])
  .paginate('.next_page@href')
  .limit(3)
  .then(function(res) {
    console.log(res[0]) // prints first result
  })
  .catch(function(err) {
    console.log(err) // handle error in promise
  })

xray.paginate(selector)

Select a url from a selector and visit that page.

xray.limit(n)

Limit the amount of pagination to n requests.

xray.abort(validator)

Abort pagination if validator function returns true. The validator function receives two arguments:

result: The scrape result object for the current page.
nextUrl: The URL of the next page to scrape.

xray.delay(from, [to])

Delay the next request between from and to milliseconds. If only from is specified, delay exactly from milliseconds.

var x = Xray().delay('1s', '10s')

xray.concurrency(n)

Set the request concurrency to n. Defaults to Infinity.

var x = Xray().concurrency(2)

xray.throttle(n, ms)

Throttle the requests to n requests per ms milliseconds.

var x = Xray().throttle(2, '1s')

xray.timeout (ms)

Specify a timeout of ms milliseconds for each request.

var x = Xray().timeout(30)

Collections

X-ray also has support for selecting collections of tags. While x('ul', 'li') will only select the first list item in an unordered list, x('ul', ['li']) will select all of them.

Additionally, X-ray supports "collections of collections" allowing you to smartly select all list items in all lists with a command like this: x(['ul'], ['li']).

Selector Types

X-ray supports multiple selector types to handle different data extraction needs. Each type provides unique capabilities for structuring and extracting data.

String Selectors

The most common selector type. Uses CSS-like syntax with support for attribute extraction using @.

x('http://example.com', {
  title: 'h1',                    // Extract text content
  link: 'a@href',                 // Extract href attribute
  html: '.content@html',          // Extract innerHTML
  image: 'img.logo@src'           // Extract src attribute
})

Function Selectors

Use functions for advanced extraction logic or to compose nested x-ray instances.

x('http://example.com', {
  // Custom extraction logic
  custom: function($, callback) {
    const value = $('.selector').text().toUpperCase()
    callback(null, value)
  },

  // Nested x-ray instance (crawling)
  details: x('.link@href', {
    title: 'h1',
    description: 'p'
  })
})

Array Selectors

Extract multiple elements into an array.

// Array of strings
x('http://example.com', {
  links: ['a@href']  // Returns array of all href attributes
})

// Array of objects
x('http://example.com', '.items', [{
  title: 'h2',
  price: '.price',
  link: 'a@href'
}])

RegExp Selectors

Extract data using regular expressions with capture groups.

x('http://example.com', {
  price: /\$(\d+\.\d{2})/,        // Extracts "19.99" from "$19.99"
  email: /[\w.]+@[\w.]+\.\w+/,    // Extracts email address
  orderId: /Order #([A-Z0-9-]+)/  // Extracts order ID from text
})

RegExp selectors return the first capture group if present, otherwise the full match. Returns null if no match is found.

Optional Fields (null/undefined)

Use null or undefined to define optional fields that always return null.

x('http://example.com', {
  title: 'h1',           // Required field
  subtitle: null,        // Optional field (always null)
  description: undefined // Optional field (always null)
})

This is useful for defining a consistent schema where some fields may not always be present.

Custom Type Handlers

const x = Xray()

// Define a custom type
function PriceType(selector) {
  this.selector = selector
}

// Register the handler
x.type('price', function(value, $, scope, filters, callback) {
  const text = $(value.selector).text()
  const price = parseFloat(text.replace(/[^0-9.]/g, ''))
  callback(null, isNaN(price) ? null : price)
}, function(value) {
  return value instanceof PriceType
})

// Use the custom type
x('http://example.com', {
  price: new PriceType('.price')
})(function(err, result) {
  console.log(result.price) // Returns numeric price
})

Strict Mode

Enable strict type validation during development to catch selector type errors:

const x = Xray({ strict: true })

x('http://example.com', {
  title: 'h1',
  invalid: 123  // Throws TypeError in strict mode
})

TypeScript Support

X-ray now includes TypeScript definitions for type-safe scraping:

import XRay = require('@hmb-research/x-ray')

interface Article {
  title: string
  author: string
  price: string | null
}

const xray = XRay()
const result = await xray('http://example.com', '.article', [{
  title: 'h2',
  author: '.author',
  price: /\$(\d+\.\d{2})/
}])

// result is typed as Article[]

Composition

X-ray becomes more powerful when you start composing instances together. Here are a few possibilities:

Crawling to another site

var Xray = require('@hmb-research/x-ray')
var x = Xray()

x('http://google.com', {
  main: 'title',
  image: x('#gbar a@href', 'title') // follow link to google images
})(function(err, obj) {
  /*
  {
    main: 'Google',
    image: 'Google Images'
  }
*/
})

Scoping a selection

var Xray = require('@hmb-research/x-ray')
var x = Xray()

x('http://mat.io', {
  title: 'title',
  items: x('.item', [
    {
      title: '.item-content h2',
      description: '.item-content section'
    }
  ])
})(function(err, obj) {
  /*
  {
    title: 'mat.io',
    items: [
      {
        title: 'The 100 Best Children\'s Books of All Time',
        description: 'Relive your childhood with TIME\'s list...'
      }
    ]
  }
*/
})

Filters

Filters can specified when creating a new Xray instance. To apply filters to a value, append them to the selector using |.

var Xray = require('@hmb-research/x-ray')
var x = Xray({
  filters: {
    trim: function(value) {
      return typeof value === 'string' ? value.trim() : value
    },
    reverse: function(value) {
      return typeof value === 'string'
        ? value
            .split('')
            .reverse()
            .join('')
        : value
    },
    slice: function(value, start, end) {
      return typeof value === 'string' ? value.slice(start, end) : value
    }
  }
})

x('http://mat.io', {
  title: 'title | trim | reverse | slice:2,3'
})(function(err, obj) {
  /*
  {
    title: 'oi'
  }
*/
})

Examples

selector: simple string selector
collections: selects an object
arrays: selects an array
collections of collections: selects an array of objects
array of arrays: selects an array of arrays

In the Wild

Levered Returns: Uses x-ray to pull together financial data from various unstructured sources around the web.

Resources

Video: https://egghead.io/lessons/node-js-intro-to-web-scraping-with-node-and-x-ray

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT