Loop / While / For / Condition / Increment / Decrement

Comparison Operators: Evaluating Conditions

You can evaluate a situation by comparing one value in the script to what you expect it might be. The result will be a Boolean true or false

value	value
>	<
greater than	less than
this operator checks if the number on the left is greater than the number on the right.	this operator checks if the number on the left is less than the number on the right.
4 > 3 returnstrue	4 < 3 returnsfalse
3 > 4 returnsfalse	3 < 4 returnstrue

Refer to Docket JavaScript Textbook page 150 Descicions and loops for:

( == ) is equal to ( === ) strict equal to ( != ) is not equal to ( !== ) strict not equal to ( > ) greater than ( < ) less than ( >= ) greater than or equal to ( >= ) less than or equal to

Loop counters

for (var i = 0; < 10; i++) { This is a for loop the condition is a counter that counts to ten.

document.write(i); The result would write “0123456789” to the page. }

Initialization	Condition	Update
create a variable and set it to0. This variable is commonly called i, and it acts as the counter	the loop should continue to run until the counter reaches a specified counter.	Every time the loop has run the statements in the curly braces, it adds one to the counter.
var i = 0;	i > 10;	i++
the variable is only created the first time the loop is run. variable (i) also referred to asindex	the value ofi was initially set to 0, so in this case the loopwill run 10 times before stopping.	one is added to the counter using the (++) operator.

Logical Operators

&& Logical And

This operator tests more than one condition

((2 < 5) && (3 >= 2))

returns true

If both expressions evaluate to true then the expression returns true. If just one of these returns false, then the expression will return false.

true && true returns true

true && false returns false

false && true returns false

false && false returns false

|| Logical or

((2 > 5) || (2 < 1>)

returns true

This operator tests at least one condition.
If either expression evaluates to true, then the expression returns true. If both return false, then the expression will return false. then the expression will return false.

true || true returns true

true || false returns true

false || true returns true

false || false returns false

!Logical Not

!(2 < 1)

returns true

This operator takes a single boolean value and inverts it.
This reverses the state of an expression. If it was false
(without the ! before it) it would return true.
If the statement was true, it would return false.

!true return false

!false returns true

Logical Operations are evaluated left to right. If the first condition can provide enough information to get the answer, then there is no need to evaluate the second condition.

Computer Logic and Loops

*Term*	Context
Loop	loops check a condition. If it returnstrue, a code block will run. Then the condition will be checked again and if it still returns true, the code block will run again. It repeats until the condition returns false. there are three common types of loops: for : while : do while
for	If you need to run code a specific number of times, use afor loop. (it is the most common loop.) In a for loop,the condition is usually a counter which is used to tell how many times the loop should run.
while	If you do not know how many times the code should run, you can usewhile loop. Here the condition can be something other than a computer,and the code will continue to loop for as long as the condition is true.
do while	thedo…while loop is very similar to the *while* loop, but has one key difference: it will always run the statements inside the curly braces at least once, even if the condition evaluates to false.
Loop Counters	afor loop uses a counter as a condition. This instructs the code to run a specified number of times. *The condtion is made up of three statements:* initialization (ph1) : condtion (ph2): update (ph3)
Condition	the loop should continue to run until the counter reaches a specified number.
Increment	guide
Decrement	see [guide] above

Read

Duckett: JavaScript & jQuery:

Comparison and logical operators: 150-151, 156, and 157
for and while loops: 170 - 173, and 176

Code 102 Table of Contents

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