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CheerioCrawler <JSONData>

Provides a framework for the parallel crawling of web pages using plain HTTP requests and cheerio HTML parser. The URLs to crawl are fed either from a static list of URLs or from a dynamic queue of URLs enabling recursive crawling of websites.

Since CheerioCrawler uses raw HTTP requests to download web pages, it is very fast and efficient on data bandwidth. However, if the target website requires JavaScript to display the content, you might need to use PuppeteerCrawler or PlaywrightCrawler instead, because it loads the pages using full-featured headless Chrome browser.

CheerioCrawler downloads each URL using a plain HTTP request, parses the HTML content using Cheerio and then invokes the user-provided CheerioCrawlerOptions.requestHandler to extract page data using a jQuery-like interface to the parsed HTML DOM.

The source URLs are represented using Request objects that are fed from RequestList or RequestQueue instances provided by the CheerioCrawlerOptions.requestList or CheerioCrawlerOptions.requestQueue constructor options, respectively.

If both CheerioCrawlerOptions.requestList and CheerioCrawlerOptions.requestQueue are used, the instance first processes URLs from the RequestList and automatically enqueues all of them to RequestQueue before it starts their processing. This ensures that a single URL is not crawled multiple times.

The crawler finishes when there are no more Request objects to crawl.

We can use the preNavigationHooks to adjust gotOptions:

preNavigationHooks: [
    (crawlingContext, gotOptions) => {
        // ...
    },
]

By default, CheerioCrawler only processes web pages with the text/html and application/xhtml+xml MIME content types (as reported by the Content-Type HTTP header), and skips pages with other content types. If you want the crawler to process other content types, use the CheerioCrawlerOptions.additionalMimeTypes constructor option. Beware that the parsing behavior differs for HTML, XML, JSON and other types of content. For details, see CheerioCrawlerOptions.requestHandler.

New requests are only dispatched when there is enough free CPU and memory available, using the functionality provided by the AutoscaledPool class. All AutoscaledPool configuration options can be passed to the autoscaledPoolOptions parameter of the CheerioCrawler constructor. For user convenience, the minConcurrency and maxConcurrency AutoscaledPool options are available directly in the CheerioCrawler constructor.

Example usage:

// Prepare a list of URLs to crawl
const requestList = await RequestList.open(null, [
    { url: 'http://www.example.com/page-1' },
    { url: 'http://www.example.com/page-2' },
]);

// Crawl the URLs
const crawler = new CheerioCrawler({
    requestList,
    async requestHandler({ request, response, body, contentType, $ }) {
        const data = [];

        // Do some data extraction from the page with Cheerio.
        $('.some-collection').each((index, el) => {
            data.push({ title: $(el).find('.some-title').text() });
        });

        // Save the data to dataset.
        await Dataset.pushData({
            url: request.url,
            html: body,
            data,
        })
    },
});

await crawler.run();

Hierarchy

Index

Constructors

Properties

Methods

Constructors

constructor

  • All CheerioCrawler parameters are passed via an options object.

    Type parameters

    • JSONData = Dictionary<any>

    Parameters

    Returns CheerioCrawler<JSONData>

Properties

optionalautoscaledPool

autoscaledPool?: AutoscaledPool

A reference to the underlying AutoscaledPool class that manages the concurrency of the crawler.

NOTE: This property is only initialized after calling the crawler.run() function. We can use it to change the concurrency settings on the fly, to pause the crawler by calling autoscaledPool.pause() or to abort it by calling autoscaledPool.abort().

readonlyconfig

config: Configuration = ...

optionalproxyConfiguration

proxyConfiguration?: ProxyConfiguration

A reference to the underlying ProxyConfiguration class that manages the crawler’s proxies. Only available if used by the crawler.

optionalrequestList

requestList?: RequestList

A reference to the underlying RequestList class that manages the crawler’s requests. Only available if used by the crawler.

optionalrequestQueue

requestQueue?: RequestQueue

Dynamic queue of URLs to be processed. This is useful for recursive crawling of websites. A reference to the underlying RequestQueue class that manages the crawler’s requests. Only available if used by the crawler.

readonlyrouter

router: RouterHandler<CheerioCrawlingContext<JSONData>> = ...

Default Router instance that will be used if we don’t specify any requestHandler. See router.addHandler() and router.addDefaultHandler().

optionalsessionPool

sessionPool?: SessionPool

A reference to the underlying SessionPool class that manages the crawler’s sessions. Only available if used by the crawler.

readonlystats

stats: Statistics

A reference to the underlying Statistics class that collects and logs run statistics for requests.

Methods

addRequests

getRequestQueue

  • Returns Promise<RequestQueue>

run

use

  • use(extension: CrawlerExtension): void

  • EXPERIMENTAL Function for attaching CrawlerExtensions such as the Unblockers.

    Parameters

    • extension: CrawlerExtension

      Crawler extension that overrides the crawler configuration.

    Returns void

useState

  • useState<State>(defaultValue?: State): Promise<State>

  • Type parameters

    • State: Dictionary<any> = Dictionary<any>

    Parameters

    • defaultValue: State = ...

    Returns Promise<State>