What is Hoisting in JavaScript?

In JavaScript, hoisting is a behavior in which variable and function declarations are moved to the top of their containing scope (either global or function scope) during the compilation phase before the code is executed. This means that you can use variables and functions before they are actually declared in the code.

Key Points of Hoisting:

Variable Hoisting:

• Variables declared with var are hoisted, but their initialization is not. This means that the declaration is moved to the top of the scope, but the assignment remains in its original place.
• Variables declared with let and const are also hoisted, but they are not initialized. Accessing them before their declaration will result in a ReferenceError. This is due to the temporal dead zone (TDZ), the period between entering the scope and the variable being declared.

The above code is interpreted by JavaScript as:

Function Hoisting:

1. • Function declarations are hoisted entirely, meaning that you can call the function before it is defined in the code.
   • Function expressions, whether using var, let, or const, are not fully hoisted, only the variable is. The function is not available until the expression is executed.

This is interpreted as:

Summary

• Declarations (variables and functions) are hoisted.
• Initializations (variable assignments) are not hoisted.
• Function declarations are fully hoisted, while function expressions are not.

Understanding hoisting helps avoid potential bugs and makes it clear why certain errors, like ReferenceError, occur when accessing variables before they are declared.