Built in objects in javascript

In this article we will learn about built in objects in JavaScript like Array, Date, Math, String and Number and the methods in them.

 

Introduction

 

To solve different kinds of problems, JavaScript provides various built-in objects. Each object contains properties and methods. Some of the built-in objects in Javascript are:

• Array
• Date
• Math
• String
• Number

 

Array object

 

The properties available on Array object are:

 

Property	Description
length	Returns the number of elements in the array
constructor	Returns the function that created the array object
prototype	Allows us to add properties and methods to an array object

 

Methods available on Array object are:

 

Method	Description
reverse()	Reverses the array elements
concat()	Joins two or more arrays
sort()	Sort the elements of an array
push()	Appends one or more elements at the end of an array
pop()	Removes and returns the last element
shift()	Removes and returns the first element
unshift()	Adds one or more elements at the beginning of an array
join()	Combines the elements of an array by a specified separator
indexOf()	Returns the first index of specified element
lastIndexOf()	Returns the last index of specified element
slice(startindex, endindex)	Returns selected elements

 

Math object

 

The Math object provides a number of properties and methods to work with Number values. Among the methods there are sin and cos for trigonometric functions, floor and round for truncating and rounding the given numbers and max for returning the maximum of given numbers.

 

Properties available on Math object are:

 

Property	Description
PI	The value of Pi
E	The base of natural logarithm e
LN2	Natural logarithm of 2
LN10	Natural logarithm of 10
LOG2E	Base 2 logarithm of e
LOG10E	Base 10 logarithm of e
SQRT2	Square root of 2
SQRT1_2	Square root of 1/2

 

Methods available on Math object are:

 

Method	Description
max(a,b)	Returns largest of a and b
min(a,b)	Returns least of a and b
round(a)	Returns nearest integer
ceil(a)	Rounds up. Returns the smallest integer greater than or equal to a
floor(a)	Rounds down. Returns the largest integer smaller than or equal to a
exp(a)	Returns ea
pow(a,b)	Returns ab
abs(a)	Returns absolute value of a
random()	Returns a pseudo random number between 0 and 1
sqrt(a)	Returns square root of a
sin(a)	Returns sin of a (a is in radians)
cos(a)	Returns cos of a (a is in radians)

 

Date object

 

At times you there will be a need to access the current date and time and also past and future date and times. JavaScript provides support for working with dates and time through the Date object.

 

Date objected is created using the new operator and one of the Date’s constructors. Current date and time can be retrieved as shown below:

var today = new Date( );

 

Methods available on Date object are:

 

Method	Description
Date()	Creates a Date object with the current date and time of the browser’s PC
Date(“Month,dd,  yyyy hh:mm:ss”)	This creates a Date object with the specified string
Date(“Month dd, yyyy”)	This creates a Date object with the specified string
Date(yy,mm,dd,hh,mm,ss)	This creates a Date object with the specified string
Date(yy,mm,dd)	This creates a Date object with the specified date
Date(milliseconds)	Creates a Date object with the date value represented by the number of milliseconds since midnight on Jan 1, 1970
getFullYear()	Returns the 4-digit year component of the date.
getMonth()	Returns the month component of the date.
getDate()	Returns the date component of the date.
getDay()	Returns the day component of the date
getHours()	Returns the hours component of the date
getMinutes()	Retrieves the minutes component of the date
getSeconds()	Retrieves the seconds component of the date
getMilliseconds()	Returns the milliseconds component of the date
getTimezoneOffset()	Retrieves the difference, in minutes, between the computer’s local time and GMT
setFullYear()	Sets the year component of the date using a 4-digit number
setMonth()	Sets the month component of the date
setDate()	Sets the day-of-month component of the date
setHours()	Set the hours component of the date
setMinutes	Set the minutes component of the date
setSeconds()	Sets the seconds component of the date
setMilliseconds()	Sets the milliseconds component of the date

 

String object

 

A string is a collection of characters. Most of the times in scripts, there is a need to work with strings. JavaScript provides various properties and methods to work with String objects. Whenever a String property or method is used on a string value, it will be coerced to a String object.

 

One most frequently used property on String objects is length. The length property gives the number of characters in the given string. Consider the following example:

var str = “Hello World”;

var len = str.length;

 

The value stored in the len variable will be 11 which the number of characters in the string.

 

Methods available on String objects are:

 

Method	Description
anchor()	Create a HTML anchor element around the specified string
big()	Create a HTML big element around the specified string
charAt(index)	Returns the character at specified index
charCodeAt(index)	Returns the unicode value of the character at specified index
concat()	Combines two or more strings
indexOf(searchtext, index)	Searches for the specified string from the beginning of the string.
lastIndexof(searchtext, index)	Searches for the specified string from the end of the string
match(expr)	Searches for a specified string in the given string and returns an array of matched strings
replace(expr, new-string)	Replaces the old string with the specified new string
search(expr)	Searches for the string/regular expression and returns its index
slice(start, end)	Extracts the sub string between the specified indices
split(delimiter, count)	Split the string into an array of substrings delimited by the delimiter
substr(start, length)	Returns a substring having length characters from a specified index
toUpperCase()	Returns the string after converting all characters to upper case
toLowerCase()	Returns the string after converting all characters to lower case

 

Number Object

 

The number object contains a collection of useful properties and methods to work with Numbers. The properties include: MAX_VALUE (represents largest number that is available), MIN_VALUE (represents smallest number that is available), NaN (represents Not a Number), POSITIVE_INFINITY (special value to represent infinity), NEGATIVE_INFINITY (special value to represent negative infinity) and PI (represents value of π.

 

To test whether the value in a variable is NaN or not, there is a method isNaN( var ), which returns true if the value in the specified variable is NaN and false otherwise. To convert a Number to a String, use the method toString( ) as shown below:

var cost = 250;

var output = cost.toString( );