What is Function and how many types of functions are there in JavaScript?

The function is a simple piece of code that can be used again and again it looks like a variable but is actually a piece of code.

There are 3 types of function

1. Function declaration.
2. Function expression.
3. Arrow function.

1. Let's have a look at Function declaration

How to write it?

A function declaration is simply declaring the function with a name and if you want to pass a parameter inside you can use it inside brackets.

Note: Function declaration can be called even before creating it. Meaning you can call the function name first and then you can create a function with the same name. This is because of Hoisting

2. Let's have a look at Function expression

It is simply a function that can be written as an expression.

How to write it?

Again here it's similar if you want to pass a parameter you simply pass inside the bracket same as the function declaration. you simply can use the return keyword to return the output.
Note: The only difference between function declaration and expression is this function cannot be called before declaring it because hoisting is not applied to this. It is a good practice to use function expression to avoid bugs and errors because you need to declare all the functions before assigning the value

3. Let's have a look at the Arrow function

The arrow function is simply the shorter form of the function made in ES6 to write it easily. How to write?

Note: In the arrow function If the argument is 1 liner then you don't have to use the return keyword but if the arguments inside the body are more than 1 line then use the return keyboard to return the value.

Important: All function have their own use a declaration can be declared even before it is actually created while a function expression can only be called once it is created and an arrow function also cannot be called before it is created.