how count occurneces of a letter in a string in javascript code example

Example 1: how do i count the number of occurrences in a string javascript

function charCount(myChar, str) {
	let count = 0;

	for (let i = 0; i < str.length; i++) 
    if (str.charAt(i) == myChar) 
        count++
 return count;
}

Example 2: how to count specific letters in string js

console.log(("str1,str2,str3,str4".match(/,/g) || []).length); //logs 3

console.log(("str1,str2,str3,str4".match(new RegExp("str", "g")) || []).length); //logs 4