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3.5 JAVASCRIPT DATATYPES
A variable or object’s capacity to store different types of data is categorised by its datatype. When computer
programmers design applications, datatypes must be referred to and used properly on both desktop and web
applications to ensure the application’s functionalities produce accurate, error-free results.
There are several datatypes. Some of them are described in detail as follows:
Datatypes Description Example
String denotes textual data “pizza”, “APPLE”
Number an integer or a floating-point number 3.25, 450
Boolean true or false value true/false
undefined a datatype with uninitialised variables var x;
null represents a null value var b = null;
Object Allows to store collection of data x = {firstname:”Suman”,
lastname:”Nagpal”};
In this case, all datatypes are primitive with the exception of Object, which is a non-primitive datatype.
Let us now study the various datatypes in detail.
Numbers
JavaScript uses double-precision 64-bit numbers. Addition, subtraction, modulus (or residual) arithmetic, and
other common numeric operations are provided. Additionally, a built-in object called Math is available to
handle more complex mathematical constants and functions.
Syntax:
var a = 16;
var num=new Number(value);
The various functions used to explicitly convert data to numbers are as follows:
Method Description Example
Number( ) Converts any value to number. NaN Number(false) Output:0
is returned if the value cannot be Number(“34”) Output:34
converted. Number(“6 5 7”) Output:NaN
parseInt( ) This method accepts two arguments parseInt(“30 years”)
and returns an integer value. Output: 30
Syntax: parseInt(string, radix) parseInt(“20.43”)
string—The value that has to be Output: 20
parsed (required) parseInt(“He is 30 years”)
radix—The default value is 10. Output: NaN
The number system is specified by parseInt(“20”, 8)
numbers 2–36. (Optional) Output: 16
parseFloat( ) The parseFloat() method returns the parseFloat(“45.5”)
first decimal number after parsing a Output: 45.5
value as a string. NaN is returned if the parseFloat(“44 56”)
initial character cannot be converted. Output:44
186 Touchpad Web Applications-XII

