What are the phases of execution context?

The execution context in JavaScript is a data structure that stores the information necessary for executing a piece of code. It includes the code itself, the values of the variables used in the code, and the scope chain. The scope chain is a list of objects that are used to resolve variable names.

The execution context has two phases:

• Creation phase: In this phase, the JavaScript engine creates the execution context and sets up the script's environment. This includes creating the variable object and the scope chain.
• Execution phase: In this phase, the JavaScript engine executes the code in the execution context. This includes evaluating expressions, assigning values to variables, and calling functions.

The execution context is created when a function is called. The function's code is then executed in the execution context. When the function returns, the execution context is destroyed.

Practical Code Example

// Phases of Execution Context:
// Phase 1: Creation Phase
// - Memory allocation for variables (var = undefined, let/const in TDZ)
// - Function declarations hoisted in entirety
// - Sets up scope chain and 'this' binding

// Phase 2: Execution Phase
// - Code executed line by line, assigns variable values, invokes functions