How to find the number of occurrences of chars in a string

Recently, I came across a code challenge to find the number of occurrences of a character in a string.

It was intended to use it as a validator in order to perform some minimum char length along with the occurrences.

Anyhow, it took some time to figure out a way using Regex.

searchString
	// split into each characters.
	.split('')
	// Sort it so that the similar chars can be grouped together.
	.sort()
	// Join them to group.
	.join('')
	// match the chars those have more than one occurrence.
	.match(/(.)\1+/g)
	// Do what you wish with the result. 
	// I am just counting the length here.
	.map((a) => a.length)

Try to modify the Regex to match only a set of chars occurrences.