Data types

JavaScript is a dynamically typed language, meaning that there exist data types, but variables are not bound to any of them.
```
// no error
let message = "hello";
message = 123456;
```
Number
- The number type represents both integer and floating point numbers.
- Besides regular numbers, there are so-called “special numeric values” which also belong to this data type: Infinity, -Infinity and NaN.

A BigInt value is created by appending n to the end of an integer.

// the "n" at the end means it's a BigInt
const bigInt = 1234567890123456789012345678901234567890n;

String
- A string in JavaScript must be surrounded by quotes.
```
let str = "Hello";
```
- More in Fundamentals Part 2.
Boolean
- This type is commonly used to store yes/no values: true means “yes, correct”, and false means “no, incorrect”.
The 'null' value
- It’s a special value which represents “nothing”, “empty” or “value unknown”.
- It forms a separate type of its own which contains only the null value:
```
let age = null;
```
The “undefined” value
- The meaning of undefined is “value is not assigned”.
- It makes a type of its own, just like null:
```
let age;

alert(age); // shows "undefined"
```
Objects and Symbols
- objects are used to store collections of data and more complex entities.
- The symbol type is used to create unique identifiers for objects.
The typeof operator
- The typeof operator returns the type of the operand.
- Usually used as typeof x, but typeof(x) is also possible.