# Hoisting in JavaScript

Before going into Hoisting let us see in how many ways we can declare a function in JavaScript.

### 1. Function Declaration :

We will write a simple function which adds two numbers and logs the sum in console.

`function sum(a, b){
console.log(a+ b)
};`

### 2. Function Expression :

`const sum=function(a, b){
console.log(a+ b)
};`

### 3. Arrow Function :

`const sum=(a, b)=>{console.log(a+ b)};`

**Hoisting** is a mechanism in JavaScript in which the function declarations are moved to the top of their scope before code execution

```
let x = 15;
let y = 10;
let result = add(x, y);
console.log(result); // 25

function add(a, b) {
   return a + b
};

``` 


When we try to implement the same function using function expression we will get a Reference Error as Function expressions are not Hoisted. Check the below code:
 

```
let x = 15;
let y = 10;
let result = add(x, y);
console.log(result); // **Reference Error** { Cannot access 'add' before initialization }

const add=function(a, b) {
   return a + b
};
``` 
Similarly Arrow functions are also not hoisted in JavaScript, We will get a below error:

```
let x = 15;
let y = 10;
let result = add(x, y);
console.log(result); // **Reference Error** { Cannot access 'add' before initialization }

const add=(a, b)=> {
return a + b;
};
```

When you have reached till here, I hope you've gone through the blog and this is my first blog which I wanted write for a longtime. Before writing this I thought Someone might have already written on this topic but felt let me write it for myself as notes. I tried to put what I have understood on this particular concept , If you find any errors/missing out do let me know I would love to learn.