Variables in JavaScript do not have a “fixed type”.

Once you assign a value of some type to a variable, you can later reassign the variable to host a value of any other type, without any issue.

In JavaScript, we have 2 main kinds of types: primitive types and object types.

Primitive types are:

• numbers
• strings
• booleans
• symbols

And two special types: null and undefined.

Any value that’s not of a primitive type (a string, a number, a boolean, null, or undefined) is an object.

We’ll talk more about objects later on.

The main difference I mention now about primitive types and objects is that objects are passed by reference, while primitive types are passed by value. This is a concept that will be useful when we’ll introduce functions.

Lessons in this unit:

0:	Introduction
1:	Literals, identifiers and variables
2:	Comments
3:	The difference between let, const and var
4:	▶︎ Types
5:	Operators and expressions
6:	Let's start with arithmetic operators
7:	The assignment operator
8:	Operators precedence
9:	Strings
10:	Numbers
11:	Semicolons, white space and sensitivity