Javascript Arrays and Loops

let a = [1,2,3,4,6,10]

What is a.length

• 1

• 4

• 10

• 6

Answer explanation

a is a variable that holds the array [1,2,3,4,6,10].

.length is a property of an array that returns the number of elements in the array

let a = [1,2,3,4,6,10]

What is a called

• variable

• array

• letter

• 6

Answer explanation

a by itself is just a variable. What a is saving a reference to is array in this case.

[1,2,3,4,6,10]

What is this called

• array

• numbers

• list

• variable

Answer explanation

an array is a list is elements seperated by commas and surrounded by square brackets[ ]

let a = [1,2,3,4,6,10]

How can I get the 3rd element

• 3

• a(3)

• 3a

• a[3]

Answer explanation

to get any element in an array you simply need to use the variable that hold the array and elements index that you wish to access.

array[7]: this will return the 8th element in the array

What does let do

• declaration

• assignment

• re-assignment

• variable

Answer explanation

let, var and const are 3 ways to declare varables

What does = do?

• assignment

• declaration

• variable

• comparison

Answer explanation

= can be confusing in JS

a single = is an assignment or saving a reference to something into a variable

a double == is comparing to see if two things are nearly the same i.e. "7" == 7 true

a triple === is comparing t see if two things are exactly the same i.e. "7" === 7 false

What does === do?

• re assignment

• variable

• comparison

• declaration

Answer explanation

= can be confusing in JS

a single = is an assignment or saving a reference to something into a variable

a double == is comparing to see if two things are nearly the same i.e. "7" == 7 true

a triple === is comparing t see if two things are exactly the same i.e. "7" === 7 false

let a = 4

a=5

return a

What will this code return?

• 4

• 5

• 6

• none

Answer explanation

the first line declares a variable and assigns a value to it. The second line re-assigns a different value to the variable. The third line returns the value that the variable is holding.

let a = 4

a===5

return a

What will this code return?

• 4

• 5

• 6

• none

Answer explanation

The first line declares and assigns a value to a variable. The second line compares a variable to a value. The third line returns the value in the variable

return 4===4

what will this return?

• 4

• none

• true

• false

Answer explanation

=== is a comparison