What is Hoisting in JavaScript?

Hoisting is a fundamental JavaScript concept where variable and function declarations are moved to the top of their scope during compilation. While it might seem like declarations are physically "lifted," JavaScript actually processes them before executing the code.

How Hoisting Works

1. Variable Hoisting

• var: Hoisted and initialized with undefined.

  console.log(x); // undefined (not an error)
  var x = 5;
  

• let/const: Hoisted but not initialized (Temporal Dead Zone).

  console.log(y); // ReferenceError
  let y = 10;
  

2. Function Hoisting

• Function declarations are fully hoisted:

  greet(); // "Hello!" (works)
  function greet() { console.log("Hello!"); }
  

• Function expressions (using var/let/const) follow variable hoisting rules.

Why Hoisting Matters

• Avoid bugs by understanding scope and initialization.
• Know why let/const are safer than var.
• Debug "undefined" vs. "ReferenceError" issues.

Best Practices

✔ Use let/const over var.
✔ Declare variables at the top of their scope.
✔ Always initialize variables before use.