count occurence js 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: javascript count occurrences in string

function countOccurences(string, word) {
   return string.split(word).length - 1;
}
var text="We went down to the stall, then down to the river."; 
var count=countOccurences(text,"down"); // 2