# Functions in JavaScript.

# Functions in JavaScript.
In JavaScript, we write code to perform a specific task or to achieve something. In Javascript, we have functions to perform a specific task. function is nothing but a block of code that performs a particular task. A function is executed when something calls it and a function is composed of statements called function body.

## Syntax

```
function sum () {
//function body
}
``` 
A Javascript function is defined with a function keyword, followed by a name, and followed by a parenthesis (). Function names can contain digits, letters, signs, etc., and parenthesis contains parameter names separated by commas.


![Untitled-2022-10-31-1812.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1668768134623/8scW2zA1K.png align="left")

***we have declared a function named message(). To use a function, we have to call it.***

### Example

```
function add () {
let x = 12;
let y = 12;
let z = x + y;
console.log(z);
}
add();
``` 
## Parameters and Arguments
The value which we pass inside a function is known as an argument and a parameter is a value that is passed when declaring a function.

### Example


```
function add (x, y) {
let z = x + y;
console.log(z);
}
add(12, 12);
``` 

![Untitled-2022-11-18-1624.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1668769675307/pp59JS_la.png align="left")

## Ways to write the function

```
function user () {
let first_Name = 'vikas';
console.log(first_Name);
}
user();
``` 

```
var user = function () {
let first_Name = "vikas";
console.log(first_Name);
}
user();
``` 

```
var user = () => {
let name = "vikas";
}
user();
``` 

## Function statement/Declaration


```
function call () {
console.log("ineuron");
}
``` 
## Function expression


```
let call = function () {
console.log("ineuron");
}
``` 
***here storing function into call and function can also be defined as expressions***

## Function with return

The return statement can be used to return the value to a function call. It denotes that the function has ended. Any code after the return is not executed and nothing is returned the function returned an undefined value.


![Untitled-2022-11-18-1739.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1668773544378/SFsEBxtBM.png align="left")

### Example


```
function sum (math, physics, chemistry) {
var result = math + physics + chemistry;
return result;
}
let total = sum (74, 84, 92);
console.log(total);
``` 


![well-done-despicable-me.gif](https://cdn.hashnode.com/res/hashnode/image/upload/v1668773807443/pTJ0MFkgG.gif align="left")