Global and Execution Context of Javascript.

JavaScript is a popular programming language that is commonly used to create interactive web applications. Understanding the global and execution context of JavaScript is essential to writing efficient and effective code. In this blog, we will explain what these contexts are and how they work.

The Global Context:
The global context is the outermost context in JavaScript. It is the default context that is created when a script is loaded into a web page. In the global context, all code that is not contained within a function is executed. This includes variable declarations and function definitions. Variables declared in the global context are accessible from any other context in the script.Below is a code example to understand the global context of Javascript.

globalVar = "Saswat";
myFunction();
function myFunction() {
  console.log(globalVar);
}

The Execution Context:
The execution context is created whenever a function is called. Each function call creates a new execution context that has its own set of variables and functions. When a function is called, the execution context is added to the top of the call stack. The call stack keeps track of the order in which functions are called, and when a function returns, its execution context is removed from the stack.

The Variable Environment:
The variable environment is a collection of all the variables and functions that are accessible in the current context. The variable environment includes function arguments, local variables, and any variables declared in outer scopes that are accessible in the current context.

The Lexical Environment:
The lexical environment is similar to the variable environment, but it also includes information about the outer environment. The outer environment is the context in which the current context was created. This is important because it allows functions to access variables that are declared in outer scopes. The lexical environment is used to resolve variable names when they are referenced in a function.

In conclusion, the global and execution context of JavaScript are essential to writing effective and efficient code. The global context is the outermost context in JavaScript, and it is where all code that is not contained within a function is executed. The execution context is created whenever a function is called, and it includes a variable environment and a lexical environment. The variable environment is a collection of all the variables and functions that are accessible in the current context, while the lexical environment includes information about the outer environment. Understanding these concepts is crucial for writing high-quality JavaScript code.