Unit 2 Review Guide
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Javascript CircuitJavascript Circuit
UNIT 2 REVIEW GUIDE
KEY TERMS & DEFINITIONS
BooleanBoolean
A variable that can either equal true or false.
var isEven = true;
ConditionCondition
A mathematical statement that evaluates to true or false.
(x > 10)
OperatorOperator
A sign that allow us to make comparisons in a condition.
=, <, >
StatementStatement
Code used to perform an action.
return y;
CollectionCollection
Groups of values and an array is an example of a collection
Type CoercionType Coercion
If the values on both sides of the double equals sign (==) have a different type (i.e., the number 1 and the
string "1"), JavaScript will try to change the type of both operands to check whether or not they are equal.
7 == "7" //returns true
ExpressionExpression
Code that is written whenever a value is expected.
y+6
Logical OperatorsLogical Operators
Operators used to combine several boolean statements into a single statement (i.e., AND, NOT, OR).
If it is raining AND I have an umbrella, then I will go outside with an umbrella.
UndefinedUndefined
A variable that is not assigned a value.
var x;
NullNull
A variable declared to have no value.
var playerScore = null;
TruthyTruthy
Something that evaluates to true, like strings, non-zero numbers, or true.
("Hello Dolly") //truthy
FalseyFalsey: Something that evaluates to false. This includes false, 0 (zero), " " (empty string), null, undefined,
or NaN (a special Number value meaning Not-a-Number).
("") //falsey
if Statementif Statement
Allows us to check whether or not a condition is true and, if it is, runs our code.
else if Statementelse if Statement
Allows us to specify a second condition to test; this second conditions will only be tested if the first
condition evaluates to false.
else Statementelse Statement
Default action taken if none of the other conditions in a code block are true.
The following code contains examples for the last three definitions:
if (answer === 38) {
// Do something if first condition is true
} else if (answer === 30) {
// Do something if second condition is true
} else {
// Do something if all above conditions are false
}
LoopLoop
A JS command that tells your program to repeat something.
while Loopwhile Loop
A loop that runs a block of code over and over again as long as our condition remains true (or at least
truthy).
while (someCondition) {
// A block of code.
}
for Loopfor Loop
A loop that runs for a fixed, controllable number of times, ensuring it will never get stuck in an infinite
loop.
for(var i = 0; i < 100; i++) {
//Note: i is not syntax but stands for any variable
//Do something for a 100 times.
}
Switch StatementSwitch Statement
A variable that gets evaluated; if there is a case listed for the value that it evaluates to, the code between
case __: and break will be executed.
var grade = "B";
switch (grade) {
case "A":
console.log("Awesome Job");
break;
case "B":
console.log("Good Job");
break;
case "V":
console.log("Okay Job");
break;
case "D":
console.log("Bad Job");
break;
case "F":
console.log("Horrible Job");
break;
default:
console.log("Nonexistent");
}
Ternary StatementTernary Statement
The one-line shorthand for an if...else statement.
var goToWork = day === "Saturday" || day === "Sunday" ? false : true;
Truth TableTruth Table
A table for determining whether something will evaluate to true or false.
A B A AND B A OR B NOT A
false false false false true
false true false true true
true false false true false
true true true true false
_____________________________________________________________________
GUIDING QUESTIONS
1. How does an if/else statement control the logic of your program?
2. What is the difference between == and ===?
3. How does boolean logic manipulate conditionals?
4. What is a for loop?
5. What is a while loop?
6. Why would we use a switch statement?
7. What is a ternary statement?
________
LOGICAL OPERATORS AND COMMANDS
Command Description
< Less than
> Greater than
<= Less than or equal to
>= Greater than or equal to
=== Strict equal to
== Equal to
!== Strict not equal to
!= Not equal to
|| OR
&& AND
! NOT
break; Exit function (necessary in switch statements)
null Used to declar variable to have no value
