> For the complete documentation index, see [llms.txt](https://eleven-fifty-academy.gitbook.io/javascript-101-fundamentals/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://eleven-fifty-academy.gitbook.io/javascript-101-fundamentals/1-javascript-fundamentals/1-js-fundamentals/4-functions/calling-functions.md).

# Calling Functions

So far, we have been defining functions and calling them. It's important to know that calling the function is what actually performs the act of running the function.

## Rules

1. Functions can be called recursively(inside itself).
2. Functions can be called inside of other functions.

## File Location

We will be working in the following file:

```
    javascript-library
        └── 0-PreWork
        └── 1-Fundamentals
            └── 1-Grammar-and-Types
            └── 2-ControlFlow-and-ErrorHandling
            └── 3-Loops
            └── 4-Functions
                03-calling-functions.js <----You will be working in this file.
```

## Example

Let's look at an example of a function that multiplies a number times itself.

1. We declare the function:
2. We call the function

   ```javascript
   //1
   function getSquare(number){
    return number * number;
   }
   //2
   getSquare(5);
   ```

## Hoisting Review

Functions must be in scope when they are called, but the function declaration can be hoisted (appear below the call in the code), as in this example:

```javascript
console.log(addNumbers(5,7));
/* ... */
function addNumbers(a, b) { return a + b; }
```

The scope of a function is the function in which it is declared, or the entire program if it is declared at the top level.

## Function Expressions

Remember that function expressions can't be hoisted. This works only when defining the function using the above syntax (i.e. function funcName(){}). The code below will not work. That means, function hoisting only works with function declaration and not with function expression.

1. Notice below that a function expression is getting created.&#x20;
2. The function is being called. It will throw an error saying addNumbers is not a function.

```javascript
//2
console.log(square(5, 7)); 

//1
var addNumbers = function(a, b) { 
  return a + b; 
}
```

## Recursion

A recursive function calls itself. We'll talk more about recursion later. Also, this timer could be done with a while loop, but for demo purposes, this works:

```javascript
var timer = function(seconds){
    if (seconds > 0){
        console.log(seconds)
        return timer(seconds-1)
    }else{
        return seconds
    }
}

timer(10);
```