# Declarations

There are three kinds of declarations in JS.

1. `var` declares a variable.
2. `let` declares a variable that is block-scoped (more on this later).
3. `const` declares a block-scoped variable, that is a constant.

## Variables

A variable is a container of memory that holds a value. _Declaring_ a variable is as simple as writing `var myVariable;`. A variable can be declared in this way, but does not have a value until it is _initialized_ by assigning it one: `myVariable = 0;`. In JavaScript we can declare a variable and initialize it at the same time: `var myVariable = 0;`. It can contain virtually anything, but it has certain naming conventions that must be followed:

1. A variable MUST begin with a letter `a-z`, an underscore `_` , or a dollar sign `$` .
2. Numbers `0-9` may follow any of these characters `h3ll0`.
3. JavaScript is a case-sensitive language: `HELLO` and `HeLLo` are two different variables.

## Declaring Variables

There are three ways to declare a variable in JavaScript:

1. The `var` keyword:  `var newVariable;`
2. Assign a variable a value: `newVariable = 12`
3. The `let` or `const` keywords: `let newVariable = 12`; `const newVariable = 12`

## File Location

```
    javascript-library
        └── 0-PreWork
        └── 1-Fundamentals
            └── 1-Grammar-and-Types
                01-comments.js
                02-declarations.js <-- You are here
```

## Practice

1. In `declarations.js`, use the `var` keyword to create two variables and assign each a value.
2. Print both variables to the console.
3. Change the values in each variable, then print both to the console again.
