The Fundamentals Flashcards
What is an expression?
A fragment of code that represents a single value, e.g. “200 + 100”, “300”
What is a statement? What is their characteristic feature?
- A fragment of code that tells the computer to do something.
- They end in a semicolon
What is a compound expression? Give an example
- An expression that contains multiple smaller expressions
- For example, “1 + 1”
What is a literal? Is “1 + 1” a literal?
- 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
The process of creating an identifier for a binding is called…
Declaration.
What are two kinds of binding that can occur in JavaScript?
- Variable: value can change
- Constant: value cannot change
Assigning a value to a variable for the first time is called…
Initialisation
List the keyword(s) that can be used to declare variables/constants
Constants: const
Variables: var & let
let Age = 5;
age = 7;
Age;
5 - JavaScript is case-sensitive with variable value assignment.
Naming convention for true variables versus self-created ones
- True: ALL_CAPS_SNAKE_CASE
- Self: camelCase
JavaScript increment/decrement operator syntax
- Increment: ++
- Decrement: –
Prefix vs postfix increment/decrement
- Prefix returns the new value immediately
- Postfix completes the same operation, but it immediately returns the value before the change anyway
What are the four main assignment operators?
- += (add another other than one “++”)
- -= subtract another other than one
- *= multiply by second expression
- /= divide by second expression
What property can we use to find the length of a string?
.length (e.g. string.length;)
What’s the syntax difference between a method and a property
- Property: .propertyName, like .length
- Method: .methodName(), like slice()
Which slice() argument is inclusive/exclusive
First: inclusive
Second: exclusive
Which method can we use to remove white space from a string?
.trim()
What is a template literal? What characters do we embed it in compared to normal? What syntax do we use to add an expression?
- A string that evaluates any expressions in it
- We enclose in backticks,
expression - To add an expression, we enclose in ${expression}
Undefined vs null
- Undefined means empty; no useful value
- Null means intentionally empty
Same functional use, different interpretation by the reader.
What are the two kinds of JavaScript operators associated with booleans?
- Logical: take/return booleans
- Comparison: take other values, return booleans
What are the three logical boolean operators? What are their JavaScript syntax?
- And: &&
- Or: ||
- Not:
Simplify !a && !b
What law is this?
!(a || b)
- From “not a and not b” to “not a or b.”
- This is De Morgan’s law
=== operator vs == operator. What is the inverse of this?
- == uses type coersion
- === does not
Both return a boolean based on whether two expressions are/aren’t equal.
Inverses are != and !==; same deal
Truthiness lets us coerce _________ values into _______ ones.
Coerce non-boolean values into booleans.
“cat” < “dog”;
Answer and explain
True.
Alphabetical order substitutes for value.
Generally speaking, what JavaScript values are falsy?
- Empty strings
- Zero
- Null/undefined
How do we check if a value is truthy? Why does this work
- Use !! operator
- First ! returns boolean inverse, second un-inverts
How do && and || operators interact w/ non-booleans?
- && 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
