Hello campers!
Here is my fifth coding challenge on medium called Alternating Characters. It is from HackerRank.
Let me know what you think of it! 
Looks good, I love how you used the Array.prototype.reduce method 
I just solved it and I remembered there’s a concept in RegExp called back-references which allow you to refer back to previously captured groups, so I thought it would be fairly easy to extract those groups of letters that are consecutive:
const nrOfDeletions = str => {
let repeated = str.match(/(\[a-z])\1+/gi)
return repeated.join('').length - repeated.length
}
All I do is take the overall count of letters that are consecutive and subtract the length of the groups array (the repeated variable) which is logically equivalent as subtracting 1 character to each group of repeated letters.
Imagine a string like “abbbaalotteec”, the number of deletions is 5 and my regex would match the following:
['bbb', 'aa', 'tt', 'ee']
The the number of deletions should be the sum of: (3-1) + (2-1) + (2-1) + (2-1) because we want to keep the first letter and get rid of the consecutive rest, that’s why I subtract one to each group.
Now on the Regex, the magic happens with: \1 which is just a reference to the first capturing group, which captures a character inside the range of a-z (both uppercase and lowercase) because of the i (case-insensitive) flag.
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