Page 189 - Web Applications (803) Class 12
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eval( ) A JavaScript expression is passed as a eval(“5*4”)
string argument to this Method. After Output: 20
that, eval( ) evaluates the expression
and returns the result. It returns
undefined if no result is received.
Unary operator ‘+’ Converts string to number + “24”
Output: 24
Other special functions include:
Output: true Description Example
isNaN( ) “Not-a-Number” is referred to as NaN in JavaScript. isNaN(“Me”)
In cases where a value is NaN, the isNaN() method Output: true
returns true.
The value is converted to a number before being isNaN(1/5)
tested by the isNaN() method. Output: false
isFinite( ) A number representing positive infinity is called
infinity. -Infinity stands for the opposite of infinity.
When a number exceeds its maximum value, it enters
infinity:
1.797693134862315E+308.
When an integer crosses its lower bound, it enters
infinity:
-1.797693134862316E+308.
If a value is a finite number, the isFinite() method Number.isFinite(“27”)
gives a true result. Output: false
Infinity, -Infinity, and NaN are examples of infinite Number.isFinite(653)
(not finite) values. Output: true
3.6 STRINGS
In JavaScript, strings are collections of characters. They are actually collections of Unicode characters, each
of which is represented by a 16-bit number. We only need to use a string of length 1 to represent a single
character.
Web Scripting—JavaScript 187

