how to count number of occurrences in javascript code example

Example 1: javascript Count the occurrences of a value in an array

const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);

// Examples
countOccurrences([2, 1, 3, 3, 2, 3], 2);                // 2
countOccurrences(['a', 'b', 'a', 'c', 'a', 'b'], 'a');  // 3

Example 2: count occurrences of character in string javascript

var temp = "This is a string.";
var count = (temp.match(/is/g) || []).length;
console.log(count);

Output: 2

Explaination : The g in the regular expression (short for global) says to search the whole string rather than just find the first occurrence. This matches 'is' twice.

Example 3: 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 4: count value a to b character javascript

let counter = str => {
  return str.split('').reduce((total, letter) => {
    total[letter] ? total[letter]++ : total[letter] = 1;
    return total;
  }, {});
};

counter("aabsssd"); // => { a: 2, b: 1, s: 3, d: 1 }