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# Web Site Writing Basics

# variable # data atype

# javascrip

Datatype in JavaScript is the type of values that a variable can store. Knowing and understanding data types allows you to act on them correctly.

Primitive Data Types

JavaScript has 7 basic data types:

String 📝

Used to store text or sequence of characters.

Must be surrounded by single (') or double (") quotation marks or Backticks (") for Template Literals

Example: 'Hello world', "JavaScript," Name: ${name}

Number 🔢

Used to store numbers, both integers and decimals.

There are special values like Infinity, -Infinity and NaN (Not a Number).

Example: 10, 3.14, -50

BigInt 🐘

Used to store integers larger than the Number can support (over 2

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－ 1)

Must be appended to the letter n.

Example: 9007199254740991n, 12345678901234567890n

Boolean ✅

It is used to store logical values. There are only two values: true (true) and false (false).

Often used in decision making (Conditional logic)

Example: true, false

Undefined. ❓

Refers to a variable that has already been declared but has not yet been configured.

It is the default value of the recently announced variable.

Example: Let x; / / x have an undefined value.

Null. 🚫

It means no value or empty value.

The developer determines that value itself to show that the variable does not have any value.

Example: let data = null;

Symbol ✨

It is a data type added to ES6 (ECMAScript 2015).

Used to create unique identifiers to use as Object properties.

Reference Data Type (Non-Primitive / Reference Data Type)

JavaScript has the main reference data types:

Object 🧱

Used to store collections of complex data (key-value pairs)

It is the foundation of complex data structures in JavaScript, including Array and Function.

Example:

Plain Object: let person = {name: "Alice," age: 30};

Array: let colors = ["red," "green," "blue"]; (Technically, an Array is a kind of Object)

Function: function greet () {/ * code * /} (Function is also considered a kind of Object)

Remarks:

Primitive types store value directly (By value)

Reference types store a reference (Address) to the location of the value in memory (By reference).

Understanding these data types is critical in writing accurate and efficient JavaScript code!