How to iterate through an array starting from the last element? (Ruby)

Question

I came with below solution but I believe that must be nicer one out there ...

array = [ 'first','middle','last']

index = array.length
array.length.times { index -= 1; puts array[index]}

Answer 1

Ruby is smart

a = [ "a", "b", "c" ]
a.reverse_each {|x| print x, " " }

Answer 2

In case you want to iterate through a range in reverse then use:

(0..5).reverse_each do |i|
  # do something
end

Answer 3

You can even use a for loop

array = [ 'first','middle','last']
for each in array.reverse do
   print array
end

will print

last
middle
first

Answer 4

If you want to achieve the same without using reverse [Sometimes this question comes in interviews]. We need to use basic logic.

1. array can be accessed through index
2. set the index to length of array and then decrements by 1 until index reaches 0

3. output to screen or a new array or use the loop to perform any logic.

       def reverseArray(input)
         output = []
         index = input.length - 1 #since 0 based index and iterating from 
         last to first
   
         loop do
           output << input[index]
           index -= 1
           break if index < 0
         end
   
         output
       end
   
       array = ["first","middle","last"]
   
       reverseArray array #outputs: ["last","middle","first"]
   

Answer 5

In a jade template you can use:

for item in array.reverse()
   item

Answer 6

You can use "unshift" method to iterate and add items to new "reversed" array. Unshift will add a new item to the beginning of an array. While << - adding in the end of an array. Thats why unshift here is good.

array = [ 'first','middle','last']
output = []
                             # or: 
for item in array            #     array.each do |item|
  output.unshift(item)       #       output.unshift(item)            
end                          #     end

puts "Reversed array: #{output}"

will print: ["last", "middle", "first"]

Answer 7

We can also use "until":

index = array.length - 1
    
until index == -1
   p  arr[index]
   index -= 1
end