Data Types

There are several types of data you may encounter in JavaScript.

Primitives

Boolean: Can only have a value of true or false. You may sometimes use a boolean as a "flag" for turning functionality on or off.
String: Used to store text information, this is a set of characters.
Number: Numerical information. Technically there are limits to how large or small of a number can safely be stored in a Number value, but it is unlikely you will encounter those limits during bootcamp.
BigInt: Used for numbers beyond the safe size limits of a Number. You will not need this during bootcamp (or maybe ever).
Undefined: This value has not been set. No information is available.
Null: An explicit way to signify that a value is empty.
Symbol: A special built-in object that is guaranteed to be unique. You will not need these for bootcamp (or maybe ever).

Four labeled images. 1. "Non-zero value" label above an image of a roll of toilet paper on a wall-mounted holder. 2. "0" label above an image of the same wall-mounted paper holder with an empty cardboard tube. 3. "null" label above an image of the same wall-mounted paper holder but no roll of any kind on it. 4. "undefined" label above an image of the blank wall only. No paper and no holder.

Objects

There are many types of data in JavaScript which are Objects, including Dates, Sets, WeakMaps and more. However, the main types that you'll use in bootcamp include:
- "Normal" objects: Constructed of "key-value pairs" describing the properties of an object. An object begins and ends with curly braces, and key-value pairs are separated by commas. Values can be of any type. For example, an object representing a person might look like
```
{
  name: 'Hercules',
  age: 18,
  todo: ['muck stables', 'slay hydra', 'get girdle']
}
```
- Array: A set of elements separated by commas. Elements of an array are often of a similar type and structure to each other. Begins and ends with square brackets. For example
```
[1, 3, 5, 7]
```
```
['do', 're', 'mi', 'fa', 'sol', 'la', 'ti', 'do']
```

Resources

The Mozilla Developer Network has a really good explanation of JavaScript data types.

Node.js

First-class Functions