# Function Declarations Vs Function Expressions

It's necessary for a developer who is new to JavaScript functions to understand the difference between function declarations and function expressions. This article will shed more light on them.

## Function Declaration

Function declarations are just normal functions. They are also referred to as function statements. A few things to note about them are:

a. They must have a function name.

b. They are standalone constructs

c. Functions in the function declaration can be accessed before and after the function definition.

```javascript
/* Function Declaration syntax */

function addNum (paramA, paramB) {
  //set of statements
}
```

```javascript
function myFunction(a1,  a2) {
  console.log(a1 * a2);
}
myFunction(2, 3);  //This line can also be placed above the function

//Logs out '6' to the console
```

## Function Expression

Function expression :

a. does not have function names

b. can be stored in a variable assignment

c. can load only when the interpreter reaches the line of code

```javascript
// Function Expression syntax

var addNum = function(paramA, paramB) {
   //set of statements
}
```

```javascript
var addNum = function (a, b) {
  console.log(a + b);
}
addNum(5, 7); //This line can only be placed after the function
```

Live code on how Functions are used

%[https://replit.com/@DEBORAHFABUSUYI/Blackjack-card-game] 

## Main Differences

1. Function declaration loads before any code is executed, while a Function expression loads when the interpreter reaches that line of code.
    
2. Function expressions are stored in a variable assignment.
    

## When to Choose a Function Declaration Vs a Function Expression

Wondering when to choose between a function declaration and a function expression?

Below are a few guidelines to help make a quick decision.

Use a Function declaration when:

1. you need to create a more readable and understandable function.
    
2. you need to create a function that is recursive (a recursive function is a function that calls itself).
    
3. you need to call the function before it is defined.
    

Use a Function expression when:

1. you need a reusable function.
    
2. the function should be used when it is defined.
    
3. you need a function that isn't hoisted ([Hoisting explained](https://www.w3schools.com/js/js_hoisting.asp#Declare%20Your%20Variables%20at%20The%20Top%20!)).
    
4. you want to control when the function is executed
    
5. the function is anonymous.
    

## Conclusion

As we've seen, both functions are similar and they share almost the same syntax. Whichever one you decide to use is totally fine.