Experimental version of Apify Web Scraper with Chrome debugger integrated

• How it works
• Getting Started
• Input
• Page function
• context
  • Data structures
  • Functions
  • Class instances and namespaces
    • Request
    • Response
    • Global Store
    • Log
    • Underscore
• Output
  • Dataset

How it works

Web Scraper is a ready-made solution for scraping the web using the Chrome browser. It takes away all the work necessary to set up a browser for crawling, controls the browser automatically and produces machine readable results in several common formats.

Underneath, it uses the Puppeteer library to control the browser, but you don't need to worry about that. Using a simple web UI and a little of basic JavaScript, you can tweak it to serve almost any scraping need.

Getting Started

If you're new to scraping or Apify, be sure to visit our tutorial to walk you through creating your first scraping task step by step.

Input

Input is provided via the pre-configured UI. See the tooltips for more info on the available options.

Page function

Page function is a single JavaScript function that enables the user to control the Scraper's operation, manipulate the visited pages and extract data as needed. It is invoked with a context object containing the following properties:

1const context = {
2    // USEFUL DATA
3    input, // Unaltered original input as parsed from the UI
4    env, // Contains information about the run such as actorId or runId
5    customData, // Value of the 'Custom data' scraper option.
6
7    // EXPOSED OBJECTS
8    request, // Apify.Request object.
9    response, // Response object holding the status code and headers.
10    globalStore, // Represents an in memory store that can be used to share data across pageFunction invocations.
11    log, // Reference to Apify.utils.log
12    underscoreJs, // A reference to the Underscore _ object (if Inject Underscore was used).
13
14    // EXPOSED FUNCTIONS
15    setValue, // Reference to the Apify.setValue() function.
16    getValue, // Reference to the Apify.getValue() function.
17    saveSnapshot, // Saves a screenshot and full HTML of the current page to the key value store.
18    waitFor, // Helps with handling dynamic content by waiting for time, selector or function.
19    skipLinks, // Prevents enqueueing more links via Pseudo URLs on the current page.
20    enqueueRequest, // Adds a page to the request queue.
21    jQuery, // A reference to the jQuery $ function (if Inject JQuery was used).
22
23}

context

The following tables describe the context object in more detail.

Data structures

Functions

The context object provides several helper functions that make scraping and saving data easier and more streamlined. All of the functions are async so make sure to use await with their invocations.

Class instances and namespaces

The following are either class instances or namespaces, which is just a way of saying objects with functions on them.

Request

Apify uses a request object to represent metadata about the currently crawled page, such as its URL or the number of retries. See the Request class for a preview of the structure and full documentation.

Response

The response object is produced by Puppeteer. Currently, we only pass the HTTP status code and the response headers to the context.

Global Store

globalStore represents an instance of a very simple in memory store that is not scoped to the individual pageFunction invocation. This enables you to easily share global data such as API responses, tokens and other. Since the stored data need to cross from the Browser to the Node.js process, it cannot be any kind of data, but only JSON stringifiable objects. You cannot store DOM objects, functions, circular objects and so on.

globalStore supports the full Map API , with the following limitations:

• All methods of globalStore are async. Use await.
• Only string keys can be used and the values need to be JSON stringifiable.
• map.forEach() is not supported.

Log

log is a reference to Apify.utils.log. You can use any of the logging methods such as log.info or log.exception. log.debug is special, because you can trigger visibility of those messages in the scraper's Log by the provided Debug log input option.

Underscore

Underscore is a helper library. You can use it in your pageFunction if you use the Inject Underscore input option.

Output

Output is a dataset containing extracted data for each scraped page. To save data into the dataset, return an Object or an Object[] from the pageFunction.

Dataset

For each of the scraped URLs, the dataset contains an object with results and some metadata. If you were scraping the HTML <title> of Apify and returning the following object from the pageFunction

1return {
2  title: "Web Scraping, Data Extraction and Automation - Apify"
3}

it would look like this:

1{
2  "title": "Web Scraping, Data Extraction and Automation - Apify",
3  "#error": false,
4  "#debug": {
5    "requestId": "fvwscO2UJLdr10B",
6    "url": "https://apify.com",
7    "loadedUrl": "https://apify.com/",
8    "method": "GET",
9    "retryCount": 0,
10    "errorMessages": null,
11    "statusCode": 200
12  }
13}

You can remove the metadata (and results containing only metadata) from the results by selecting the Clean items option when downloading the dataset.

The result will look like this:

1{
2  "title": "Web Scraping, Data Extraction and Automation - Apify"
3}