Reference

Array Methods

Methods available on Ruby Array objects.

1. Array#all?

   Checks if all elements in an array match a condition. Returns true if every element satisfies the block or is truthy.

   arr.all? { |element| block } -> true or false
2. Array#any?

   Checks if any element in an array matches a condition. Returns true if at least one element satisfies the block or is truthy.

   arr.any? { |element| block } -> true or false
3. Array#append

   Adds one or more elements to the end of an array, mutating it in place. Returns the same array object.

   arr.append(*objects) -> arr
4. Array#assoc

   Searches an array of arrays for the first sub-array with a matching first element.

   array.assoc(key) -> sub_array or nil
5. Array#bsearch

   Binary search for elements in a sorted array. Supports find-minimum and find-any modes for efficient O(log n) lookups.

6. Array#bsearch

   Binary search for elements in sorted arrays using .bsearch in Ruby. Find elements in O(log n) time.

   arr.bsearch { |x| block } -> obj or nil
7. Array#combination

   Generate all combinations of array elements. combination selects unordered arrangements of a given size.

   arr.combination(n) { |c| block }
8. Array#compact

   Removes all nil values from an array. The bang variant compact! mutates the original array in place and returns nil if no changes were made.

9. Array#compact

   Removes nil values from an array, returning a new array. The destructive variant modifies the array in place.

   arr.compact -> array
10. Array#delete

    Remove elements from arrays by value in Ruby. delete removes all matching elements and returns the removed value.

    arr.delete(obj) -> obj or nil
11. Array#delete_at

    Remove elements from arrays by index in Ruby. delete_at removes the element at a specific position and returns it.

    arr.delete_at(index) -> obj or nil
12. Array#detect

    Returns the first element in an array or enumerable that matches a condition, or nil if nothing matches. Alias for find.

    arr.detect { |element| block } -> obj or nil
13. Array#difference

    Returns a new array containing elements that are not present in the given arrays.

14. Array#drop

    Returns all elements except the first n elements from an array.

    arr.drop(n) -> array
15. Array#drop_while

    Skips elements from the beginning of an array while the block returns truthy.

    arr.drop_while { |element| block } -> array
16. Array#each_index

    Learn how Ruby Array#each_index yields positions instead of elements, when to use it, and how it compares with each_with_index.

    array.each_index { |index| block } -> array
17. Array#each_slice

    Split arrays into consecutive or sliding windows with each_slice and each_cons

18. Array#find

    Returns the first element in an array or enumerable that matches a condition, or nil if nothing matches.

    arr.find { |element| block } -> obj or nil
19. Array#first

    Returns the first element of an array, or the first n elements as a new array.

    arr.first(n=nil) -> obj or array
20. Array#flatten

    Recursively flattens a nested array into a single array. Use flatten(level) to limit depth, or flatten! to mutate in place.

21. Array#flatten

    Returns a new array with all nested arrays recursively collapsed into a single flat array.

    arr.flatten(depth=nil) -> array
22. Array#flatten_map

    Combines map and flatten(1) into one method. Transforms each element and flattens the result by one level.

23. Array#flatten!

    Flattens a nested array in place, converting multi-dimensional arrays to single-dimensional.

    array.flatten!(level=nil) -> array or nil
24. Array#inject

    Combines all elements by applying a binary operation, accumulating a running result. Also known as reduce in other languages.

    inject(initial = nil) { |memo, element| block } -> result
25. Array#intersection

    Returns a new array containing elements common to all arrays, preserving duplicates from the first array.

26. Array#intersection

    Returns a new array containing elements common to all arrays, removing duplicates. The & operator provides the same functionality.

    array & other_array -> array
27. Array#join

    Joins array elements into a string separated by a given delimiter. Converts each element to a string recursively for nested arrays.

    arr.join(separator=nil) -> string
28. Array#last

    Returns the last element of an array, or the last n elements as a new array.

    arr.last(n=nil) -> obj or array
29. Array#map

    Returns a new array with the results of running a block on every element. Also available as collect, an exact synonym, and map! for in-place mutation.

30. Array#map

    Transform array elements with map and collect methods in Ruby. Returns a new array with the results of running the block once for each element.

31. Array#max

    Find maximum and minimum elements in Ruby arrays using .max, .min, and .minmax methods.

32. Array#none?

    Checks if no elements in an array match a condition. Returns true if no element satisfies the block or is truthy.

    arr.none? { |element| block } -> true or false
33. Array#one?

    Checks if exactly one element in an array matches a condition. Returns true if precisely one element satisfies the block or is truthy.

    arr.one? { |element| block } -> true or false
34. Array#permutation

    Generate all permutations of array elements. permutation selects ordered arrangements of a given size.

    arr.permutation(n) { |p| block }
35. Array#pop

    Removes and returns the last element of an array. Mutates the array in place. With an argument, removes and returns the last n elements as a new array.

36. Array#pop

    Add and remove elements from array ends. pop/shift remove, push/unshift add.

    arr.pop(n=nil) -> obj or array
37. Array#prepend

    Adds one or more elements to the beginning of an array, mutating it in place. Returns the same array object.

    arr.prepend(*objects) -> arr
38. Array#product

    Generate the cartesian product of arrays in Ruby. Creates all possible combinations from multiple arrays.

39. Array#push

    Appends one or more elements to the end of an array. Mutates the array in place and returns self.

40. Array#reduce

    Combines all elements by applying a binary operation, accumulating a running result. Alias for inject.

    reduce(initial = nil) { |memo, element| block } -> result
41. Array#reject

    Returns a new array containing all elements for which the block evaluates to false. The bang variant reject! mutates the original array in place.

42. Array#reject

    Filter out elements from an array based on a condition. Returns a new array excluding elements for which the block returns true.

    arr.reject { |element| block } -> new_array
43. Array#reverse

    Returns a new array with elements in reverse order. Available in Ruby 1.8+.

44. Array#rotate

    Returns a new array with elements rotated so the element at the given offset becomes the first element. The bang variant rotates in place. O(n) time complexity.

45. Array#rotate

    Rotates array elements in place, returning a new array with elements shifted. Available in Ruby 1.9.2+.

46. Array#sample

    Returns one or more random elements from an array. With an argument n, returns an array of up to n unique elements chosen at random.

47. Array#sample

    Randomly select elements with .sample or shuffle array order with .shuffle in Ruby.

48. Array#select

    Returns a new array containing all elements for which the block evaluates to true. The bang variant select! mutates the original array in place.

49. Array#select

    Filter array elements based on a condition. Returns a new array containing only elements for which the block returns true.

    arr.select { |element| block } -> new_array
50. Array#shift

    Removes and returns the first element of an array, or the first n elements as an array. O(n) since all subsequent elements must be shifted down by one position.

51. Array#size

    Returns the number of elements in a collection (strings, arrays, hashes) or characters in a string.

    collection.size -> integer
52. Array#sort

    Sort array elements by value or custom criteria in Ruby

53. Array#sum

    Sum array elements with the .sum method in Ruby. Returns the sum of all elements, with optional initial value.

54. Array#take

    Extract or skip elements from the beginning of an array. take returns first n elements, drop skips first n, and the _while variants use a block condition.

    arr.take(n) -> array
55. Array#take_while

    Returns elements from the beginning of an array while the block returns truthy.

    arr.take_while { |element| block } -> array
56. Array#tally

    Count occurrences of each element in an array. Returns a hash where keys are elements and values are their counts.

57. Array#tally

    Counts the occurrence of each element in an array and returns a hash.

58. Array#union

    Returns a new array containing all elements from self and given arrays, duplicates removed. Added in Ruby 3.1.

59. Array#uniq

    Returns a new array with duplicate elements removed. Supports a block for custom uniqueness logic. The bang variant uniq! mutates the array in place.

60. Array#uniq

    Remove duplicate elements from arrays in Ruby with uniq method. Returns a new array with unique elements.

61. Array#zip

    Combines two or more arrays element-by-element into an array of tuples using zip in Ruby. Pairs corresponding elements, filling shorter arrays with nil.

62. Array#zip

    Combines each element from self with corresponding elements from each given array.