In this lesson we learned how to use commentaries and variables.

Javascript works with dynamic typing in variables.

The variable identifiers must follow some rules:

1. They must begin with a letter, $ or _;
2. They can't begin with a number;
3. It's possible to use letters and numbers;
4. It's possible to use accents and symbols;
5. They can't contain spaces;
6. They can't be reserved words.

1. number: stores the all types of numbers. Includes two special types: Infinity and NaN.
2. string: stores a characters array.
3. boolean: stores the logic data.
4. null: indicates that the variable have a null value.
5. undefined: indicates that the variable type is undefined.
6. object: stores an object. The Array type is an object.
7. function: indicates a function.

Typeof is a function that return the type of the variable passed as argument.