JavaScript Date

What is the Date Object?

The Date object in JavaScript is used to work with dates and times. It provides methods for creating, formatting, manipulating, and comparing dates.

Creating Date Objects

1. Current Date and Time

let now = new Date();
console.log(now); // Output: current date and time

2. Specific Date

let birthday = new Date("1995-12-17");
console.log(birthday); // Output: Sun Dec 17 1995 ...

3. With Year, Month, Day, etc.

let customDate = new Date(2023, 0, 15, 10, 30); // Jan is 0
console.log(customDate); // Output: Sun Jan 15 2023 10:30:00 ...

Date Methods

Method	Description	Example Output
getFullYear( )	Gets the year	2024
getMonth()	Gets the month (0–11)	0 for January
getDate()	Gets the day of the month (1–31)	15
getDay()	Gets the day of the week (0–6)	0 for Sunday
getHours()	Gets hours (0–23)	10
getMinutes()	Gets minutes (0–59)	30
getSeconds()	Gets seconds (0–59)	45
getTime()	Gets time in milliseconds since 1970	1700000000000 (example)
toDateString ()	Converts to readable date string	"Mon Jan 15 2024"
toISOString( )	Converts to ISO 8601 format	"2024-01-15T08:30:00.00 0Z"

Example: Get Current Components

let today = new Date();
console.log(today.getFullYear()); // Output: 2024
console.log(today.getMonth()); // Output: 0 (Jan)
console.log(today.getDate()); // Output: 15

Modifying Dates

let date = new Date();
date.setFullYear(2030);
date.setMonth(11); // December
console.log(date); // Output: updated date

JavaScript RegExp (Regular Expressions)

What is a RegExp?

A Regular Expression (RegExp) is a pattern used to match character combinations in strings.

It is commonly used for searching, validating, and replacing text.

Syntax

let pattern = /abc/;
let result = pattern.test("abc123");
console.log(result); // Output: true

You can also use the constructor:

let pattern = new RegExp("abc");

Common RegExp Methods

Method	Description	Example Output
test()	Returns true if match is found	true
exec()	Returns match object or null	[ 'abc' ]
match()	Returns match (used with strings)	["abc"]
replace( )	tdReplaces matched text	str.replace()
search()	Returns index of match	5
split()	Splits string by pattern	str.split()

Basic RegExp Patterns

Pattern	Description	Matches
.	Any single character	"a" , "1"
\d	Any digit (0–9)	"3" , "7"
\w	Any word character (a–z, A–Z, 0–9, _)	"a" , "Z" , "0" , " _ "
\s	Whitespace	space, tab, newline
^abc	Starts with "abc"	"abc123"
abc$	Ends with "abc"	"123abc"
` a	b`	"a" or "b"
[abc]	Any of a, b, or c	"a" , "b"
[^abc]	Not a, b, or c	"d" , "x"
a*	0 or more a's	"" , "a" , "aaaa"
a+	1 or more a's	"a" , "aa"
a?	0 or 1 a	"" , "a"
{n}	Exactly n times	a{3} matches "aaa"
{n,}	At least n times	a{2,} matches "aa" , "aaa"
{n,m}	Between n and m times	a{2,4} matches "aa" , "aaa"

Example: Email Validation

let email =
"test@example.com";
let pattern = /^[\w.
-]+@[\w.
-]+\.\w+$/;
console.log(pattern.test(email)); // Output: true

Example: Replace Digits

let str =
"abc123";
let result = str.replace(/\d/g,
"*");
console.log(result); // Output: abc***

Example: Split by Space

let sentence =
"JavaScript is awesome";
let words = sentence.split(/\s/);
console.log(words); // Output: ["JavaScript", "is", "awesome"]

Recap: RegExp vs Date

Feature	Date	RegExp
Use Case	Work with time and calendar	Pattern matching in strings
Constructor	new Date()	new RegExp() or /pattern/
Output Type	Object	Boolean or Array