What Is JavaScript?
A scripting language that allows you to add automation, interactivity, and animations to web pages and applications. It is used by the most popular websites such as Google, Facebook, and YouTube to give users a more interactive experience on their sites. It is also used to provide 2D and 3D graphics, video, real-time content updates, and responsive user interfaces.
It is a client-side programming language, meaning that it can only be run within the context of a browser. The browser executes and interprets the JavaScript, which makes it more efficient than a server-side language that needs to be executed on a remote machine. The browser also controls the execution environment, which makes it possible for JS to access resources on the computer that it is running in.
The JavaScript engine processes the code by parsing it into a data structure called an abstract syntax tree (AST). This AST is then translated to machine codes, which are converted to 0’s and 1’s by the processor. The code is then pushed into the call stack and executed by the browser, which executes it in the context of an execution environment called the runtime. The runtime is a set of global variables and functions that are accessible to the function being executed.
Once the runtime is loaded, it begins to create a scope chain, which contains all of the variable objects and function declarations that are available for the current function. Each variable object has a name that is used to identify it, and its value is assigned during the execution of the function. The value of the ‘this’ variable is set to the current object during the execution of the function, and it provides the context for which the function is being executed.
When a variable is not initialized, the runtime assigns a default value to it, usually in the form of an integer. This default value is known as the value of the variable, and it can be accessed by other functions that may need to know its value. The default value can be changed at any time by the programmer, who can also change the name of a variable to something more meaningful.
If a variable’s value is a string, it must be enclosed in double quote marks. Other types of values, such as numbers and the truth value (“False”), do not require quotation marks. Functions in JavaScript may take any number of arguments, and these are passed to the function by using the var or let keyword before the variable name, with each argument being separated by commas if there is more than one.
Several factors affect the performance of a JavaScript code, including how often the DOM is manipulated and how many function calls are made. By minimizing DOM manipulation and reducing function calls, developers can help to optimize the performance of their code. This is especially important when working with large or complex scripts, as each function call takes up valuable runtime.