### .Js

## Data Types

Data types represent the kind of data that can be used and manipulated within a program. Here are the primary data types in JavaScript:

### Primitive Data Types:

**1.** __Number__: Represents numeric values, including integers and floating-point numbers.

**2.** __String__: Represents sequences of characters, enclosed within single *('')*, double *("")* or backticks *(``)*.

**3.** __Boolean__: Represents a logical value, either *'true'* or *'false'*.

**4.** __Undefined__: Represents a variable that has been declared but not assigned a value.

**5.** __Null__: Represents an intentional absence of any object value.

**6.** __Symbol (added in ECMAScript 6)__: Represents a unique and immutable value, often used as object property keys.

**7.** __BigInt (added in ECMAScript 2020)__: Represents integers of arbitrary precision, useful when working with very large numbers.

### Composite Data Types:

**1.** __Object:__ Represents a collection of key-value pairs, where values can be accessed by keys. Objects can be created using object literals *'{}'*, constructors, or classes.

**2.** __Array__: Represents a list-like collection of elements, which can be of any data type. Arrays are ordered and can be accessed by index. They are created using array literals *'[]'*.

**3.** __Function__: Represents executable code. Functions are objects in JavaScript, and they can be assigned to variables, passed as arguments, and returned from other functions.

**4.** __Date__: Represents dates and times.

**5.** __RegExp__: Represents regular expressions for pattern matching with strings.

### Special Data Types:

**1.** __NaN__: Represents "Not-a-Number" value, returned when a mathematical operation is performed, but the result is not a valid number.

**2.** __Infinity and -Infinity__: Represent positive and negative infinity, returned when a number exceeds the upper limit of the floating-point numbers.

**Note:** JavaScript is a dynamically typed language, meaning you don't need to specify the data type of a variable explicitly; it is inferred by the interpreter.

Tabular representation of JavaScript data types:

Data Type | Description | Example |
---|---|---|

Number | Represents numeric values, including integers and floating-point numbers. | let num = 42; |

String | Represents sequences of characters. | let str = 'Hello' |

Boolean | Represents a logical value, either 'true' or 'false' |
let bool = true; |

Undefined | Represents a variable that has been declared but not assigned a value. | let undefinedVar; |

Null | Represents an intentional absence of any object value. | let nullVar = null; |

Symbol | Represents a unique and immutable value, often used as object property keys. | const sym = Symbol(); |

BigInt | Represents integers of arbitrary precision. | const bigIntNum = 123n; |

Object | Represents a collection of key-value pairs. | const obj = {}; |

Array | Represents a list-like collection of elements. | const arr = []; |

Function | Represents executable code. | function foo() { ... } |

Date | Represents dates and times. | const now = new Date(); |

RegExp | Represents regular expressions for pattern matching with strings. | const regex = /pattern/; |

NaN | Represents "Not-a-Number" value, returned when a mathematical operation is not a valid number. | const notANumber = NaN; |

Infinity | Represents positive infinity, returned when a number exceeds the upper limit of floating-point numbers. | const posInfinity = Infinity; |

-Infinity | Represents negative infinity, returned when a negative number exceeds the lower limit of floating-point numbers. | const negInfinity = -Infinity; |

## Keywords

JavaScript keywords are reserved words that have special meanings and purposes within the language. These keywords cannot be used as identifiers (such as variable names or function names) in JavaScript. Here's a list of JavaScript keywords .

**Note:** You cannot use these keywords as identifiers in your JavaScript code, such as variable names, function names, or labels.

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