Essential Books

Filtering arrays

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Often we want to operate only on elements of an array that fulfill a specific condition:

Select

Will return elements that match a specific condition 

array = [1, 2, 3, 4, 5, 6]
array.select { |number| number > 3 } # => [4, 5, 6]

Reject

Will return elements that do not match a specific condition 

array = [1, 2, 3, 4, 5, 6]
array.reject { |number| number > 3 } # => [1, 2, 3]

Both #select and #reject return an array, so they can be chained: 

array = [1, 2, 3, 4, 5, 6]
array.select { |number| number > 3 }.reject { |number| number < 5 }
  # => [5, 6]
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Arrays:
* Arrays
* Create Array of Strings
* Create Array with Array new
* Create Array of Symbols
* Manipulating Array Elements
* Accessing elements
* Creating an Array with the literal constructor
* Decomposition
* Arrays union intersection and difference
* Two-dimensional array
* Inject reduce
* Filtering arrays
* Arrays and the splat operator
* map
* Turn multi-dimensional array into a one-dimensional flattened array
* Get unique array elements
* Get all combinations permutations of an array
* Remove all nil elements from an array with compact
* Create an Array of consecutive numbers or letters
* Create Array of numbers
* Cast to Array from any object
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