counting occurrences of particular javascript code example

Example 1: how to count occurences in an array with javascript

// This function counts instances of elements in an array
// the return object has the array elements as keys
// and number of occurrences as it's value
const arrToInstanceCountObj = arr => arr.reduce((obj, e) => {
  obj[e] = (obj[e] || 0) + 1;
  return obj;
}, {});

arrToInstanceCountObj(['h', 'e', 'l', 'l', 'o', 'w', 'o', 'r', 'l', 'd'])
/*
  {
    h: 1,
    e: 1,
    l: 3,
    o: 2,
    w: 1,
    r: 1,
    d: 1,
  }
*/

Example 2: 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;
}