JavaScript Hoisting

JavaScript Hoisting

In JavaScript Hoisting default behavior of moving variable and function declarations to the top of their scope before execution.

This means you can use variables and functions before declaring them (but with rules).

Hoisting with `var`

Variables declared with var are hoisted but initialized as undefined.

Hoisting with `let` and `const`

let and const are hoisted but NOT initialized.
Accessing them before declaration causes an error because they are in the Temporal Dead Zone (TDZ).

Function Hoisting

Function Declarations are fully hoisting:

Function Expressions are NOT fully hoisting:

Arrow Functions behave like function expressions:

Summary Table

Declaration Type	Hoisted?	Initialized?	Can Use Before Declaration?
`var`	Yes	`undefined`	Yes (but undefined)
`let`	Yes	No (TDZ)	No
`const`	Yes	No (TDZ)	No
Function Declaration	Yes	Yes	Yes
Function Expression	Yes	No	No
Arrow Function	Yes	No	No

Best Practices

Use let and const to avoid confusion
Declare variables at the top of their scope
Avoid relying on hoisting behavior in real projects

JavaScript Hoisting