In JavaScript, a variable is a named container used to store arbitrary data referred to as a value.

It can be used to store a wide range of information, such as text, numbers, dates, errors, objects, and pretty much anything else you can think of.

Depending on certain conditions, this value may change during the execution of the script and be updated either by the developer through statements, the user through input, or the script itself through logic.

Data types

In JavaScript, variables can store multiple data types regrouped under two categories: primitive values and objects.

Primitive values

Primitive values are fundamental data types like numbers or strings, that represent individual pieces of data.

In JavaScript, there are 7 primitive value types: Boolean, Number, BigInt, String, Undefined, Null, and Symbol.

Boolean

The Boolean type represents a logical value, and holds only one of two values: true or false.

It is used for conditional checks, logical operations, and boolean-based decision making.

For example:

let isOnline = true;let isAvailable = false;

Number

The Number type represents numeric data, such as integers or floating-point numbers, both positive and negative.

It is used for arithmetic operations, calculations, and representing quantities or measurements in programs.

For example: