The JavaScript Math object allows you to perform mathematical tasks on numbers.
Math.PI;
Unlike other objects, the Math object has no constructor.
The Math object is static.
All methods and properties can be used without creating a Math object first. Continue reading JavaScript Math Object
Set Date methods let you set date values (years, months, days, hours, minutes, seconds, milliseconds) for a Date Object.
Set Date methods are used for setting a part of a date:
| Method | Description |
|---|---|
| setDate() | Set the day as a number (1-31) |
| setFullYear() | Set the year (yyyy) |
| setHours() | Set the hour (0-23) |
| setMilliseconds() | Set the milliseconds (0-999) |
| setMinutes() | Set the minutes (0-59) |
| setMonth() | Set the month (0-11) |
| setSeconds() | Set the seconds (0-59) |
| setTime() | Set the time (milliseconds since January 1, 1970) |
The setFullYear() method sets the year of a date object. In this example to 2020 : Continue reading JavaScript Set Date Methods
In JavaScript, date objects are created with new Date().
new Date() returns a date object with the current date and time.
const date = new Date();
| Method | Description |
|---|---|
| getFullYear() | Get year as a four digit number (yyyy) |
| getMonth() | Get month as a number (0-11) |
| getDate() | Get day as a number (1-31) |
| getDay() | Get weekday as a number (0-6) |
| getHours() | Get hour (0-23) |
| getMinutes() | Get minute (0-59) |
| getSeconds() | Get second (0-59) |
| getMilliseconds() | Get millisecond (0-999) |
| getTime() | Get time (milliseconds since January 1, 1970) |
The get methods above return Local time.
Universal time (UTC) is documented at the bottom of this page.
There are generally 3 types of JavaScript date input formats:
| Type | Example |
|---|---|
| ISO Date | “2015-03-25” (The International Standard) |
| Short Date | “03/25/2015” |
| Long Date | “Mar 25 2015” or “25 Mar 2015” |
The ISO format follows a strict standard in JavaScript.
The other formats are not so well defined and might be browser specific.
JavaScript Date Objects let us work with dates:
Mon Feb 24 2025 06:31:40 GMT+0330 (Iran Standard Time)
const d = new Date();
const d = new Date("2022-03-25");
Date objects are static. The “clock” is not “running”.
The computer clock is ticking, date objects are not.
In 2015, JavaScript introduced an important new keyword: const.
It has become a common practice to declare arrays using const:
const cars = ["Saab", "Volvo", "BMW"];
An array declared with const cannot be reassigned :
const cars = ["Saab", "Volvo", "BMW"];
cars = ["Toyota", "Volvo", "Audi"]; // ERROR
The keyword const is a little misleading. Continue reading JavaScript Array Const
The forEach() method calls a function (a callback function) once for each array element.
const numbers = [45, 4, 9, 16, 25];
let txt = "";
numbers.forEach(myFunction);
function myFunction(value, index, array) {
txt += value + "<br>";
}
Note that the function takes 3 arguments:
The example above uses only the value parameter. The example can be rewritten to :
const numbers = [45, 4, 9, 16, 25];
let txt = "";
numbers.forEach(myFunction);
function myFunction(value) {
txt += value + "<br>";
}
The sort() method sorts an array alphabetically:
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort();
The indexOf() method searches an array for an element value and returns its position.
Note: The first item has position 0, the second item has position 1, and so on.
Search an array for the item “Apple”:
const fruits = ["Apple", "Orange", "Apple", "Mango"];
let position = fruits.indexOf("Apple") + 1;
array.indexOf(item, start)
| item | Required. The item to search for. |
| start | Optional. Where to start the search. Negative values will start at the given position counting from the end, and search to the end. |
Array.indexOf() returns -1 if the item is not found. Continue reading JavaScript Array Search
The length property returns the length (size) of an array:
const fruits = ["Banana", "Orange", "Apple", "Mango"];
let size = fruits.length;
The JavaScript method toString() converts an array to a string of (comma separated) array values. Continue reading JavaScript Array Methods