ES6 / lodash count the number of occurrences of a character in a string

Question

I want to count the number of occurrences of a character in a string.

This stack overflow post does that using ES5 but not ES6 or Lodash:

Count the number of occurrences of a character in a string in Javascript

However, I want to know if there is a more ES6 way of doing this. Lodash solutions are also acceptable.

Answer 1

And here's a lodash solution:

const count = (str, ch) => _.countBy(str)[ch] || 0;

console.log(count("abcadea", "a"));

<script src="https://cdn.jsdelivr.net/lodash/4.17.4/lodash.min.js"></script>

The solution looks compact, does not use regular expressions and still does the job in a single scan. It must be quite fast, though if the performance is really crucial, better opt for good old for loop.

Update: Another lodash-based solution:

const count = (str, ch) => _.sumBy(str, x => x === ch)

console.log(count("abcadea", "a"));

<script src="https://cdn.jsdelivr.net/lodash/4.17.4/lodash.min.js"></script>

Answer 2

I don't think that it's better than the RegExp solutions, but it's ES6.

Spread the string to and array, and filter the result to get only the letter that you want. The length of the resulting array is the number off occurrences of that letter.

const str = "aabbccaaaaaaaccc";

const result = [...str].filter(l => l === 'c').length;

console.log(result);