What is the first step of the Critical Rendering Path?
- Construction of the CSSOM
- Parsing of the HTML and construction of the DOM
- Calculating the position and styles of each element
- Sending a GET request to the server for the page’s HTML
Explanation: The first step of the Critical Rendering Path (CRP) is indeed the Parsing of the HTML and construction of the DOM. When a browser receives an HTML document, it begins parsing the markup, turning it into a structured representation known as the Document Object Model (DOM). The DOM is a tree-like structure that represents the structure of the HTML document, with each node representing an element, attribute, or piece of text. This process is essential for the browser to understand the content and structure of the web page. As the browser parses the HTML, it also identifies external resources such as CSS and JavaScript files that need to be fetched to fully render the page. The construction of the DOM is the foundational step of the rendering process, laying the groundwork for subsequent actions such as the construction of the CSS Object Model (CSSOM), layout, painting, and rendering. Therefore, optimizing this initial step is crucial for improving overall page loading performance and ensuring a smooth user experience.