What Happens Behind the Scenes?

javascript is a computer programming language used to make web pages and applications more dynamic and interactive. It’s unique in that it can run directly in the browser, unlike hypertext markup language (HTML) and cascading style sheets (CSS). Combined with HTML, javascript creates a functional webpage displayed via a web browser. While many developers know how to write javascript code, not all understand what goes on behind the scenes when the program is parsed and executed in the browser. Understanding how this process works helps shape the way developers approach problems and adapt to future coding best practices.

When a web page designer adds a javascript element, the script is downloaded and processed by the browser on the user’s computer or device. The JS code can be embedded in the HTML code itself or stored separately as a separate.js file and referenced with a script> tag. The browser will then execute the javascript along with the associated HTML and CSS, creating a functioning page that displays in a browser tab.

Javascript is a client-side programming language, meaning that it runs in the browser rather than on a server. This makes it ideal for a variety of uses, including adding interactivity to a website, validating information entered into online forms, and providing real-time updates that can be displayed without the need to reload the entire page. Some examples include websites with news tickers, stock or crypto prices, and chat widgets.

Like other programming languages, javascript uses variables to store data, which can be either numeric (data that is added or multiplied), string (information such as names or product ID codes) or boolean (data that is true or false). The 63 different keywords in javascript allow for complex operations and comparisons.

The javascript code is compiled, translated into machine instructions and then executed in the browser. While this process is happening, a list of function calls is maintained in memory known as the Call Stack. If a function is called frequently, the engine can implement optimization strategies that speed up execution time. These techniques include minimizing DOM manipulation, reducing function calls and inlining functions.

One common problem is that javascript can be difficult to debug, since many HTML editors don’t support a robust debugger and browsers don’t display errors in the page window. Fortunately, there are several javascript debugging tools available, most notably Amazon’s AWS Cloud9, which provides a comprehensive suite of development and debugging features. Despite these challenges, learning to write efficient javascript code is a critical skill for web developers. By taking the time to understand how javascript is parsed and executed, developers can minimize code bugs, increase speed and performance, and stay on top of new trends in web design and functionality. Ultimately, this deeper level of understanding will help them build better websites and apps for their customers.