Can javascript develop crawlers?

With the popularity and development of the Internet, web crawlers have become a very important application technology. By crawling and analyzing website data, web crawlers can provide companies with very valuable information and promote their development. In the development process of crawlers, it has become a trend to use JavaScript language for development. So, can JavaScript develop crawlers? Let’s discuss this issue below.

First of all, you need to understand that JavaScript is a scripting language that is mainly used to add some interactive features and dynamic effects to web pages. Using JavaScript in web pages mainly operates HTML elements through the DOM to achieve dynamic effects. In the development of crawlers, the source code of the web page is mainly obtained through the HTTP protocol, and then the required information is extracted through a series of parsing procedures. Therefore, to put it simply, crawler development and web development are two different fields. However, JavaScript, as a scripting language with complete programming syntax, control flow and data structures, can play an important role in crawler development.

1. Use JavaScript for front-end crawler development

In front-end crawler development, JavaScript is mainly used to solve problems related to interaction with the browser and page rendering. For example, if some data needs to be obtained through Ajax and Dom operations are performed, JavaScript is a very suitable tool.

When using JavaScript for front-end crawler development, the two libraries Puppeteer and Cheerio are often used.

Puppeteer is a Node.js library based on Chromium. It simulates real browser operations so that crawlers can achieve effects similar to real user browser operations without an API. Puppeteer can simulate clicks, inputs, scrolling and other operations, and can also obtain browser window size, page screenshots and other information. Its emergence greatly facilitates the development of front-end crawlers.

Cheerio is a library for parsing and manipulating HTML. It can manipulate DOM like jQuery and provides a series of APIs to make front-end crawler development very simple and effective. The emergence of Cheerio allows us to get rid of cumbersome regular expressions and DOM operations when using JavaScript for front-end crawler development, and obtain the required information faster and more conveniently.

2. Use Node.js for back-end crawler development

When using Node.js for back-end crawler development, libraries such as request, cheerio and puppeteer are often used.

Request is a very popular Node.js HTTP client that can be used to obtain web content and other operations. It supports functions such as HTTPS and cookies, and is very convenient to use.

The use of Cheerio on the backend is similar to that on the frontend, but requires an extra step, that is, after requesting the source code from the target website, the source code is then passed to Cheerio for operation, parsing and filtering the required information.

The use of Puppeteer on the backend is similar to that on the frontend, but you need to pay attention to ensure that the target machine has the Chromium browser installed. If the Chromium browser is not installed on the target machine, you need to install it first. The process of installing the Chromium browser is also relatively cumbersome.

Summary

Therefore, it can be seen that although the JavaScript language is not a language specifically designed for crawlers, it has corresponding tool libraries for front-end and back-end crawler development. For the development of front-end crawlers, you can take advantage of libraries such as Puppeteer and Cheerio. For the development of back-end crawlers, we can use Node.js as the development language and use libraries such as request, cheerio, and puppeteer to easily implement the crawler functions we need. Of course, when using JavaScript for crawler development, you also need to abide by network legal regulations and crawler ethics, and use legal methods to obtain data.

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