Javascript Fundamentals

Question 1

How do you declare a variable?

Answer 1

let name = value

Question 2

What are the rules for naming variables?

Answer 2

can’t start with a number

can’t contain special characters except for $ and _

Question 3

What are operators, operands, and operations?

Answer 3

Operators - the symbol in an operation
Operands - The numbers
Operations - tho sum as a whole

Question 4

What is concatenation and what happens when you add numbers and strings together?

Answer 4

String concatonation is the joining of multiple strings into one string

Question 5

What is the difference between == and ===?

Answer 5

Double equals (==) is a comparison operator, which transforms the operands having the same type before comparison.

So, when you compare string with a number, JavaScript converts any string to a number. An empty string is always converts to zero. A string with no numeric value is converts to NaN (Not a Number), which returns false.
What is === in JavaScript?

=== (Triple equals) is a strict equality comparison operator in JavaScript, which returns false for the values which are not of a similar type. This operator performs type casting for equality. If we compare 2 with “2” using ===, then it will return a false value.

Question 6

What are operator precedence values?

Answer 6

BODMAS

Question 7

What are the increment/decrement operators?

Answer 7

++

–

Question 8

What is the difference between prefixing and post-fixing the increment/decrement operators?

Answer 8

the postfix form counter++ also increments counter but returns the old value (prior to increment

Question 9

What is the “Unary +” Operator?

Answer 9

+=

Question 10

What are the eight data types of javascript?

Answer 10

number - for numbers of any kind: integer or floating-point, integers are limited by ±253.
bigint - is for integer numbers of arbitrary length.
string - for strings. A string may have zero or more characters, there’s no separate single-character type.
boolean - for true/false.
null - for unknown values – a standalone type that has a single value null.
undefined - for unassigned values – a standalone type that has a single value undefined.
object - for more complex data structures.
symbol - for unique identifiers.

Question 11

Which data type is NOT primitive?

Answer 11

object

Question 12

What is the difference between single, double, and backtick quotes for strings?

Answer 12

There’s practically no difference between single and double quotes. Backtick quotes can be used to reference variables inside strings

Question 13

Which type of quote lets you embed variables/expressions into a string?

Answer 13

backtick quote

Question 14

How do you embed variables/expressions into a string?

Answer 14

${variable_name}

Question 15

How do you escape characters in a string?

Answer 15

\

Question 16

What is the difference between slice/substring/substr?

Answer 16

slice() extracts a part of a string and returns the extracted part in a new string.

substring() is similar to slice().
The difference is that substring() cannot accept negative indexes.

substr() is similar to slice().
The difference is that the second parameter specifies the length of the extracted part.

Question 17

What are methods?

Answer 17

a method is a bit of functionality that is built into the language or into specific data types

Question 18

What are the three logical operators and what do they stand for?

Answer 18

&& - AND
|| - OR
! - NOT

Question 19

What are the comparison operators?

Answer 19

== - equality
=== - strict equality
> - greater than
< - less than
>= - greater than or equal to
<= - less than or equal to

Question 20

What is nesting?

Answer 20

putting if/else statements inside other if/else statements

Question 21

What are truthy and falsy values?

Answer 21

In JavaScript, truthy are expressions which evaluates to boolean true value and falsy evaluates to boolean false value.

Question 22

What are the falsy values?

Answer 22

boolean false
empty string
undefined
null
NaN
0

Question 23

What is the syntax for an if/else conditional?

Answer 23

if (conditon) {
    code;
} else {
    code;
}

Question 24

What is the syntax for a switch statement?

Answer 24

switch (condition) {
    case evaluation:
        code;
        break;
    default:
        code;

Question 25

What is the syntax for a ternary operator?

Answer 25

(condition ? exprIfTrue : exprIfFalse);

Question 26

What is the relationship between null and undefined?

Answer 26

undefined means a variable has been declared but has not yet been assigned a value
null is an assignment value. It can be assigned to a variable as a representation of no value:

Question 27

What are conditionals?

Answer 27

statements that control whether or not a block of code will execute, if/else statements for examplelet