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The else clause is optional

Note that when writing JavaScript code, the else clause shown in Figure 5 is optional. In other words, you might choose to direct the script to take some specific action if the condition is true, but simply transfer control to thenext sequential statement in the script if the condition is false.

A selection script example

Listing 3 shows a sample script containing two selection statements (commonly called if-else statements) in sequence.

Listing 3 . A selection script example.
<!-- File JavaScript03.html --><html><body><script language="JavaScript1.3">if(3>2){ document.write("3 is greater than 2.","</br>") }else{document.write("3 is not greater than 2.") }//end ifif(3<2){ document.write("3 is less than 2.","</br>") }else{document.write("3 is not less than 2.") }//end if</script></body></html>

If 3 is greater than 2...

The conditional clause in the first if statement in Listing 3 uses the "greater-than" relational operator ">" to determine if the literal value 3 is greater than the literal value 2, producing the first line of output shown in Figure 6 .

Figure 6 . Output from script in Listing 3 .
3 is greater than 2. 3 is not less than 2.

The test returns true

Since 3 is always greater than 2, the statement in the line immediately following the first test in Listing 3 is executed and the code in the line following the word else is skipped producing the first line of output text shown in Figure 6 .

If 3 is less than 2...

The conditional clause in the second if statement in Listing 3 uses the "less-than" relational operator (see Figure 7 ) to determine if the literal value 3 is less than the literal value 2.

The test returns false

Since 3 isn't less than 2, the statement in the line immediately following the second test in Listing 3 is skipped and the statement in the line immediately following the second word else is executed producing the second line of output text shown in Figure 6 .

Relational and logical operators

I doubt that I will need to use logical operators in the modules in this collection. If I do, I will explain them at the time. However, Iwill use relational operators.

The relational operators that are supported by JavaScript are shown in Figure 7 .

Figure 7 . Relational operators.
>Left operand is greater than right operand>= Left operand is greater than or equal to right operand<Left operand is less than right operand<= Left operand is less than or equal to right operand == Left operand is equal to right operand!= Left operand is not equal to right operand

As with the arithmetic operators discussed earlier, we will use these operators extensively as we work through the physics exercises in futuremodules.

Variables

The next item in the list under Structured programming is repetition . Before I can explain repetition, however, I need to explain the use of variables.

What is a variable?

You can think of a variable as the symbolic name for a pigeonhole in memory where the script can store a value. The script can change the values stored inthat pigeonhole during the execution of the script. Once a value has been stored in a variable, that value can be accessed by calling out the name of thevariable.

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Accessible physics concepts for blind students. OpenStax CNX. Oct 02, 2015 Download for free at https://legacy.cnx.org/content/col11294/1.36
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