> For the complete documentation index, see [llms.txt](https://javascript-1.gitbook.io/javascript/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://javascript-1.gitbook.io/javascript/hoisting.md).
# Hoisting
It is a behaviour of moving variable or function declaration to the top of their environment.
* JavaScript engine looks for the var and function key as a first word's in the line of the environment, it allocates the memory var and functions in its creation phase.
* It moves the var and function to the top of the environment on creation phase.
* The variables will be partially hoisted, that means the variable is created in top as a undefined variable, but functions are fully hoisted, means complete function is moved to the top.
* EX:
| Actual Code | Hoisted code |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| console.log(text); // undefined
greet(); // hello
console.log(greet2); // undefined
console.log(greet2()); // Type Error: greet2 is not a function
var text = ‘welcome’;
function greet() {
console.log(‘Hello’);
}
var greet2 = function() {
console.log(‘Hello2’);
}
| var text = undefined;
var greet2 = undefined;
function greet() {
console.log(‘Hello’);
}
console.log(text); // undefined
greet(); // hello
console.log(greet2) // undefined
console.log(greet2()) // Type Error: greet2 is not a function
var text = ‘welcome’;
var greet2 = function() {
console.log(‘Hello2’);
}
|
**Note:** let and const will not be hoisted.
