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LearningFuze > JavaScript Concepts > Flashcards

JavaScript Concepts Flashcards

1
Q

What data type is returned by an arithmetic operation?

A

Number

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2
Q

What is string concatenation?

A

its when you combine strings using the + operator

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3
Q

What purpose(s) does the + plus operator serve in JavaScript?

A

for numbers, it acts as the addition operator. 2+ 3 = 5

for strings, it acts as a concatenator

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4
Q

What data type is returned by comparing two values < , > , === , etc )?

A

boolean, either true or false

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5
Q

What does the += “plus-equals” operator do?

A

it is a shortcut command.

if word += 5 is the same as word = word + 5

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6
Q

What is the purpose of variables?

A

to assign a value for later reference. var area = 3 * 2

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7
Q

How do you declare a variable?

A

by using the keywords var , let , const

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8
Q

How do you initialize (assign a value to) a variable?

A

by using the = sign

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9
Q

What does it mean to say that variable names are “case sensitive”?

A

if the cases in the variable name are not matched exactly, an error will show

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10
Q

What does the = operator mean in JavaScript?

A

it is used to set values of variables

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11
Q

How do you update the value of a variable?

A

by using the variable name then the equal sign, followed by new value

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12
Q

What are objects used for?

A

a collection of properties where those properties can have their own values

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13
Q

What are object properties?

A

they are variable names that are attached to the object and they can have their values. The values can be different types but the properties are strings.

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14
Q

Describe object literal notation.

A 
var obj = {
}
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15
Q

How do you remove a property from an object?

A

delete nameOfObject.PropertyToDelete

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16
Q

What are the two ways to get or update the value of a property?

A

dot notation or bracket notation

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17
Q

What data type is returned by an arithmetic operation?

A

Numbers, including NaN since its type is number

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18
Q

What is string concatenation?

A

when you condense 2 or more strings into 1 string using the + operator

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19
Q

What purpose(s) does the + plus operator serve in JavaScript?

A

for strings it will be used to concatenate
for numbers it is used to add
for string + number it will concatenate by turning the number into a string

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20
Q

What is a function in JavaScript?

A

a formula, can be customized by you to take 0, 1, or more arguments. It will return a value., if you do not use return it will return undefined

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21
Q

Describe the parts of a function definition.

A

function key word, function name, parenthesis, and parameters (optional)

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22
Q

Describe the parts of a function call.

A 
function name followed by (arguments here)
example.  greet('tom')
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23
Q

When comparing them side-by-side, what are the differences between a function call and a function definition?

A

function definition is just the code that you wrote, it will not run until it is called with ()

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24
Q

What is the difference between a parameter and an argument?

A

parameters are used when a function is declared. argument are the values that are passed into the parameters when the function is called

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25
Q

Why are function parameters useful?

A

you can use them as variables, which gives way more flexibility to do stuff

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26
Q

What two effects does a return statement have on the behavior of a function?

A

1) it ENDS the function when the JS engine finishes the return statement line
2) it returns a value from the function

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27
Q

What are arrays used for?

A

to have a collection of data by an ordered list, starting at index 0

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28
Q

Describe array literal notation

A

var = [] empty brackets mean array literal

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29
Q

How are arrays different from “plain” objects?

A

arrays do NOT have a property name and value. They have an index and a value. But like object, the value can be any type aka functions, objects, another array, number, string, etc

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30
Q

What number represents the first index of an array?

A

0

31
Q

What is the length property of an array?

A

how many items it contains = the length

32
Q

How do you calculate the last index of an array?

A

by using arrayName.length - 1

33
Q

Why do we log things to the console?

A

to check our work during development phase

34
Q

What is a method?

A

a function attached to an object as a property

35
Q

How is a method different from any other function?

A

you must call it by calling the object first, using dot notation

36
Q

How do you remove the last element from an array?

A

the pop method

37
Q

How do you round a number down to the nearest integer?

A

use Math.floor(number here)

38
Q

How do you generate a random number?

A

Math.random(numbers here) it is only from 0-.999999999999999999999

39
Q

How do you delete an element from an array?

A

use the splice method, it is the 2nd argument

40
Q

How do you append an element to an array?

A

by using splice or push

41
Q

How do you break a string up into an array?

A

the split method

42
Q

Do string methods change the original string? How would you check if you weren’t sure?

A

no they do not, you can console.log the original variable assigned the the original string to check

43
Q

Roughly how many string methods are there according to the MDN Web docs?

A

40

44
Q

Is the return value of a function or method useful in every situation?

A

most of the time yes

45
Q

Roughly how many array methods are there according to the MDN Web docs?

A

about 35

46
Q

What three-letter acronym should you always include in your Google search about a JavaScript method or CSS property?

A

MDN

47
Q

Give 6 examples of comparison operators.

A 
< 
 >
==
===
> =
< =
48
Q

What data type do comparison expressions evaluate to?

A

boolean so either true or false

49
Q

What is the purpose of an if statement?

A

to check conditions

50
Q

Is else required in order to use an if statement?

A

no

51
Q

Describe the syntax (structure) of an if statement.

A

if ( condition here ) {
code here
}

52
Q

What are the three logical operators?

A

&& (and) || (or) ! (not)

53
Q

How do you compare two different expressions in the same condition?

A

use either && or ||

54
Q

What is the purpose of a loop?

A

to check values of collection 1 by 1, you can do something during those checks

55
Q

What is the purpose of a condition expression in a loop?

A

the parameters for when the loop stops/runs

56
Q

What does “iteration” mean in the context of loops?

A

cycling through each element/value

57
Q

When does the condition expression of a while loop get evaluated?

A

at the start of the loop

58
Q

When does the initialization expression of a for loop get evaluated?

A

at the start of the loop

59
Q

When does the condition expression of a for loop get evaluated

A

after initialization

60
Q

When does the final expression of a for loop get evaluated?

A

after the condition has ran

61
Q

Besides a return statement, which exits its entire function block, which keyword exits a loop before its condition expression evaluates to false?

A

break

62
Q

What does the ++ increment operator do?

A

increases the value of the variable attached by 1

63
Q

How do you iterate through the keys of an object?

A

by using the for in loop

64
Q

What is a method?

A

a function inside an obj

65
Q

How can you tell the difference between a method definition and a method call?

A

definition is when it is being defined inside the function. A method call is requires dot notation to access the method inside the function

66
Q

Describe method definition syntax (structure).

A

propertyName : function name( parameters) {
code block
}

67
Q

Describe method call syntax (structure).

A

objName.Propertyname.methodName( )

68
Q

How is a method different from any other function?

A

it is part of an object

69
Q

What is the defining characteristic of Object-Oriented Programming?

A

writing procedural functions and storing them inside objects, which can then be accessed via dot notation

70
Q

What are the four “principles” of Object-Oriented Programming?

A

Abstraction
Encapsulation
Inheritance
Polymorphism

71
Q

What is “abstraction”?

A

being able to work with (possibly) complex things in simple ways

72
Q

What does API stand for?

A

Application Programming Interface

73
Q

What is the purpose of an API?

A

is a set of functions that allows applications to access data and interact with external software components, operating systems, or microservices

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