Converting a loop into a recursive function

Question

I wrote a function yesterday to count the number of \"a\" characters in a string. My teacher told me to refactor the code into a recursive function and I don\'t

Answer 1

Well, the basic concept of recursion is solving a problem with a smaller version of itself.

You have a function, numberOfA which gives you the length of a string(or maybe substring).

So let's say you have the string "javascript' the first string is at index 2.

It's logical to say that the number of as in your string is equal to 1 plus the number of as in the entire substring after the first a.

So what you do, is you add 1 to the number of as in the substring vascript

So here's some psudocode

function numA(str)
{
    var substring = substr(index_of_first_a, str.length - index_of_first_a
    return 1 + numA(substring);
}