JS Definitions

Question 1

What is Programming?

Answer 1

telling the computer to manipulate data

Question 2

What is a Variable?

Answer 2

named location for storing a value

Question 3

What are Comments?

Answer 3

section of code that the computer ignores
i.e. for humans to read
//
/* comment */

Question 4

What are Functions?

Answer 4

prime mechanism with which to manipulate data and usually returns a value

Functions are one of the fundamental building blocks in JS
A function is a JavaScript procedure, which is:
A set of statements that perform a task or calculate a value
A function definition (or declaration) consists of a function keyword, followed by:
The name of the function
A list of parameters to the function, enclosed in parentheses and separated by commas
The JS statements that define the function, enclosed in curly braces { }

Question 5

What is Undefined?

Answer 5

Data type in Javascript

variable is not assigned to a particular value

Question 6

what are Booleans?

Answer 6

logical value type

can be true or false

Question 7

What are Numbers?

Answer 7

only one number type in JS,
positive, negative, integer, floating point (decimal)
+Infinity ; -Infinity ; NaN

Question 8

What are some primary JS Operations / Operators?

Answer 8

\+ ; - ; * ; /
% Modulus (division remainder)
\++ Increment
-- Decrement
=
\+= ; -= ; *= ; /= ; %= ;
example x += y is x = x + y

Question 9

Explain Function vs Arguments

Answer 9

function addTwo(num) {
     return num + 2;
}

function "takes" as its parameter is num;
actual "call" to the function is addTwo(6)
6 is the "argument"

Question 10

What is a String?

Answer 10

primitive and scalar data type
stores a series of characters
"string is between quotes"
double or single quotes
index starts at 0

Question 11

What are the Primitive Data Types?

Answer 11

There are 6 primitive data types:

1. Boolean — true or false
2. Null — no value
3. Undefined — a declared variable but hasn’t been given a value
4. Number — integers, floats, etc
5. String — an array of characters i.e words
6. Symbol — a unique value that’s not equal to any other value

Question 12

What are the Collection Data Types?

Answer 12

arrays

objects

Question 13

What is an Array?

Answer 13

The array is used to store an ordered list of multiple values in a single variable
Arrays are considered “objects” in JS

Question 14

What is an Object?

Answer 14

An object is a collection of properties
A property is an association between a name (key) and a value (some data type)
A property’s value can be any of the types we have gone over, as well as being another object, or even a function
In the case where the value of a property is a function, we refer to the property as a method

Question 15

What is typeof operator?

Answer 15

One very useful tool in programming is the typeof operator

Its functionality is rather simple, and when applied to a value, it will tell you the type of value in question

Question 16

What is an Array.isArray?

Answer 16

a method to determine if a type is an array or an object

Question 17

What is an Operator?

Answer 17

An operator is used to perform specific computations or operations on operands
We have seen a few so far: =,+, -, and typeof
They can be unary: {operator} {operand} (e.g. typeof “username”), or:
They can be binary: {operand1} {operator} {operand2} (e.g. 4 + 5)
There are many more

Question 18

What is a Method?

Answer 18

A method is a function that is a property of an object
We have seen a few so far: console.log, and Array.isArray()
There are many more

Question 19

What are the falsy values?

Answer 19

1. false
2. 0
3. ””
4. null
5. undefined
6. NaN