In Ruby 2.4, how do I find the earliest index of an element of an array in another array? That is, if any element of an array occurs in the other array, I want to get the first index. I thought find_index might do it, but
a = ["a", "b", "c"]
# => ["a", "b", "c"]
a.find_index("a")
# => 0
a.find_index(["b", "c"])
# => nil
In the above example, I would expect to see the output "1" because the element "b" occurs at index 1 in the array "a".