Arrayology

Question 1

Add element to end of array

Answer 1

array.push(element)

Question 2

Remove and return element from end of array

Answer 2

array.pop(element)

Question 3

Add element to beginning of array

Answer 3

array.unshift(element)

Question 4

Remove and return element from beginning of array

Answer 4

array.shift(element)

Question 5

Find the first instance of a value

Answer 5

array.indexOf(value)

Optional second argument specifies where to start searching from.

Question 6

Find the last instance of a value

Answer 6

array.lastIndexOf(value)

Optional second argument specifies where to start searching from.

Question 7

Get me a copy of the elements between some indices

Answer 7

array.slice(start, stop)
Start is inclusive, stop exclusive. If either is omitted, the slice starts at 0 or ends at the last element, respectively.

String slicing works the same.

Question 8

How do I glue two arrays together

Answer 8

array.concat(other_array)

Question 9

String indexing??

Answer 9

string. indexOf(substring)
- -> Note: the argument for indexOf may be a whole substring, and indexOf will return the index of the start of the substring.

Question 10

How can I remove whitespace from a string?

Answer 10

string.trim()

Question 11

What about the length of an array or object or string?

Answer 11

array. length
string. length
object. length

Question 12

Reverse an array in place?

Answer 12

array.reverse()

Question 13

Apply a function to each element of an array?

Answer 13

array.forEach(function)

NOTE: the function may be user-defined, may even be defined on the spot in the call to forEach.

Question 14

Sift through the elements of an array?

Answer 14

array.filter(function) –> returns a new array with the elements of the original array for which the function argument returns true.

Question 15

Transform an array?

Answer 15

array.map(function) –> returns a new array created by applying the function to each element of the original.

Question 16

‘Sum up’ an array?

Answer 16

array.reduce(function) –> will return a single value, the result of applying the binary function to each set of values in the array.

Question 17

The fundamental higher-order functions on arrays

Answer 17

forEach
map
filter
reduce
bind
every
some

Question 18

How do I know if every element of an array has a property?

Answer 18

array.every(predicate) –> returns true iff every element of the array returns true when evaluated by the predicate function.

Question 19

How do I know if there is at least one element of an array with a given property?

Answer 19

array.some(predicate) –> returns true iff some element of the array evaluates as true when tested by the predicate function