The Fundamentals

Question 1

What is an expression?

Answer 1

A fragment of code that represents a single value, e.g. “200 + 100”, “300”

Question 2

What is a statement? What is their characteristic feature?

Answer 2

• A fragment of code that tells the computer to do something.
• They end in a semicolon

Question 3

What is a compound expression? Give an example

Answer 3

• An expression that contains multiple smaller expressions
• For example, “1 + 1”

Question 4

What is a literal? Is “1 + 1” a literal?

Answer 4

• A literal is an expression that directly corresponds to a value, like “5”
• “1 + 1” is not literally the same as 2, so is not a literal

Question 5

The process of creating an identifier for a binding is called…

Answer 5

Declaration.

Question 6

What are two kinds of binding that can occur in JavaScript?

Answer 6

• Variable: value can change
• Constant: value cannot change

Question 7

Assigning a value to a variable for the first time is called…

Answer 7

Initialisation

Question 8

List the keyword(s) that can be used to declare variables/constants

Answer 8

Constants: const
Variables: var & let

Question 9

let Age = 5;
age = 7;
Age;

Answer 9

5 - JavaScript is case-sensitive with variable value assignment.

Question 10

Naming convention for true variables versus self-created ones

Answer 10

• True: ALL_CAPS_SNAKE_CASE
• Self: camelCase

Question 11

JavaScript increment/decrement operator syntax

Answer 11

• Increment: ++
• Decrement: –

Question 12

Prefix vs postfix increment/decrement

Answer 12

• Prefix returns the new value immediately
• Postfix completes the same operation, but it immediately returns the value before the change anyway

Question 13

What are the four main assignment operators?

Answer 13

• += (add another other than one “++”)
• -= subtract another other than one
• *= multiply by second expression
• /= divide by second expression

Question 14

What property can we use to find the length of a string?

Answer 14

.length (e.g. string.length;)

Question 15

What’s the syntax difference between a method and a property

Answer 15

• Property: .propertyName, like .length
• Method: .methodName(), like slice()

Question 16

Which slice() argument is inclusive/exclusive

Answer 16

First: inclusive
Second: exclusive

Question 17

Which method can we use to remove white space from a string?

Answer 17

.trim()

Question 18

What is a template literal? What characters do we embed it in compared to normal? What syntax do we use to add an expression?

Answer 18

• A string that evaluates any expressions in it
• We enclose in backticks, expression
• To add an expression, we enclose in ${expression}

Question 19

Undefined vs null

Answer 19

• Undefined means empty; no useful value
• Null means intentionally empty

Same functional use, different interpretation by the reader.

Question 20

What are the two kinds of JavaScript operators associated with booleans?

Answer 20

• Logical: take/return booleans
• Comparison: take other values, return booleans

Question 21

What are the three logical boolean operators? What are their JavaScript syntax?

Answer 21

• And: &&
• Or: ||
• Not:

Question 22

Simplify !a && !b

What law is this?

Answer 22

!(a || b)

• From “not a and not b” to “not a or b.”
• This is De Morgan’s law

Question 23

=== operator vs == operator. What is the inverse of this?

Answer 23

• == uses type coersion
• === does not

Both return a boolean based on whether two expressions are/aren’t equal.

Inverses are != and !==; same deal

Question 24

Truthiness lets us coerce _________ values into _______ ones.

Answer 24

Coerce non-boolean values into booleans.

Question 25

“cat” < “dog”;

Answer and explain

Answer 25

True.

Alphabetical order substitutes for value.

Question 26

Generally speaking, what JavaScript values are falsy?

Answer 26

• Empty strings
• Zero
• Null/undefined

Question 27

How do we check if a value is truthy? Why does this work

Answer 27

• Use !! operator
• First ! returns boolean inverse, second un-inverts

Question 28

How do && and || operators interact w/ non-booleans?

Answer 28

• && returns the first falsy value it reads (L to R), or the final value if all are truthy
• || returns the first truthy value it finds, or the last if all are falsy