What is JavaScript?

While most people who learn to code start with HTML and CSS, javascript is the third element that makes websites and web applications dynamic. It allows developers to respond to user interactions (clicks, scrolls) and browser events (page load, resize) and it provides access to various browser APIs.

JavaScript is a general-purpose programming language whose syntax allows for the creation of object-oriented programs. It also supports multidimensional arrays and powerful built-in methods for working with these data collections. For example, there are methods to push(), pop(), shift(), unshift(), splice(), slice(), concat(), join() and more for working with arrays. These built-in functions make javascript very flexible and a good choice for working with data.

Unlike other languages that compile source code before it runs, javascript has an interpreter that runs the code as it is written. This is a great advantage as it allows developers to write, test and debug their code without needing a compiler. However, this comes with a trade-off: the interpreter must keep track of all the function calls, and this can affect performance.

To improve performance, javascript uses a technique called inlining. When a function is called multiple times, the engine substitutes the original function code with the function call itself. This reduces the number of function calls and increases speed.

The code that is compiled and executed by the javascript interpreter is first parsed to turn it into an abstract syntax tree. Then, the AST is translated into machine code using a just-in-time compiler. Finally, the code is run in a context called an execution stack. The stack keeps track of all the function calls and the state of the code that is currently running.

Most javascript code is written in a form known as procedural programming. This means that each step is determined by a conditional expression, such as if (x>y). The result of the test is a new value for x or y, which determines what will be done next. If the test fails, an error is thrown and the code stops running.

A few important features of javascript are: