Cheerio is a fast, flexible, and lean implementation of core jQuery designed specifically for the server to parse, manipulate, and render HTML. Cheerio uses a CSS selector engine to traverse the DOM and manipulate elements, but it does not have a rendering engine like a web browser. This means that pseudo-classes that depend on the visual rendering of the document (like :hover) are not supported.
However, structural pseudo-classes such as :first-child, :last-child, :nth-child(n), and others which are based on the document structure rather than user interaction states, are supported in Cheerio because they can be determined from the DOM tree itself.
Here's an example of how to use :first-child in Cheerio to select the first child element of a given parent element:
const cheerio = require('cheerio');
// Example HTML
const html = `
<ul id="my-list">
<li class="item">First item</li>
<li class="item">Second item</li>
<li class="item">Third item</li>
</ul>
`;
// Load HTML into Cheerio
const $ = cheerio.load(html);
// Select the first child of the list using :first-child pseudo-class
const firstChildText = $('#my-list > li:first-child').text();
console.log(firstChildText); // Output: First item
In this example, the :first-child pseudo-class is used to select the first <li> element within the <ul> with the ID my-list.
It's important to note that while Cheerio can handle some CSS selectors with pseudo-classes, it does so purely based on the structure of the HTML document and not on any style or state that would typically be applied by a browser during rendering. For dynamic pseudo-classes that rely on user interaction or element states (e.g., :hover, :active, :focus), you would need to execute JavaScript in a browser environment, which Cheerio does not provide.
For cases where you need to handle dynamic pseudo-classes and other browser-rendered states, you may need to use a tool like Puppeteer or Selenium, which controls a real browser and has access to the rendered state of the page.
