![]() You can have words that appear in the body of your page to a user that do not appear in the source code of the site and search engine spiders who do not render the page will be unable to detect that content. ![]() When you click it, it dynamically changes to say “Unlike” and swaps the thumbs up icon for a thumb down.Ĭontent on the page can be manipulated by JavaScript to display things in your browser that do not appear when you view a web page’s source code. When you look at it on page load, it says “Like” and shows a thumb up. This means that JavaScript code executes after the web page has been rendered and painted onto the screen, and when it executes it triggers a re-render to account for changes made.Īn example of this is the Like button on Facebook. Things like popup windows, actions that occur on a button press and elements that move across the page are all things done by JavaScript. JavaScript is a programming language which allows things to happen inside of the browser and makes web pages interactive. For Google to understand that a word on the page is in the body context of the page, it must be able to process the entire page. Painting – Each node (branch) of the render tree is drawn out on the screen by communicating with the Operating System Interface which contains designs and styles for how UI elements should look.Ī search engine spider cannot “see” a web page the way we do and will instead use a set of rules programmed into it to construct the DOM tree and understand the elements that are a part of it. This starts at the top left in position 0,0 and elements and attributes are mapped to coordinates on the screen.Ĥ. Layout Process – Once the render tree is constructed, the rendering engine recursively goes through the HTML elements in the tree and figure out where they should be placed on the screen. It communicates with the networking layer of the browser to grab HTML code and other items passed from a remote server. The rendering engine has a very important job as it displays what you see on your screen. Operating System Interface – The browser must interact with the operating system to draw out several elements of the page like drop down boxes and the chrome of a window (close, maximize, and minimize buttons). ![]() Storage – Browser’s must store some data which can include cached files, cookies, and recently browsers have updated to be able to store data and objects created with JavaScript.Network Layer – This is a function of the browser that happens behind the scenes and handles network functions such as encryption, http and ftp requests, and all network settings such as timeouts and the handling of HTTP status codes.JavaScript Engine – This engine takes JavaScript code, parses it, executes it, and returns the results.User Interface – This is the visual presentation of controls in the browser, for instance the back and forward buttons, bookmarks, and all chrome that appears around the main browser window where web pages display.For instance, a tag would be interpreted by the rendering engine as a set of instructions to make the text inside of the element bold. Rendering Engine – this takes HTML code and interprets it into what you see visually.Layout Engine – this takes input from the browser (URL bar, search box, mouse clicks and key presses) and passes them to the rendering engine.
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