JAVASCRIPT

count duplicate elements in array javascript

const counts = {};
const sampleArray = ["1", "5", "9", "14", "5", "22", "48", "25", "22", "20", "9" ,"13"]
sampleArray.forEach(function (x) { counts[x] = (counts[x] || 0) + 1; });
console.log(counts)
 // output: {
  '1': 1,
  '5': 2,
  '9': 2,
  '13': 1,
  '14': 1,
  '20': 1,
  '22': 2,
  '25': 1,
  '48': 1
}

count the number of times a same value appears in a javascript array

var arr = [2, 3, 1, 3, 4, 5, 3, 1];

function getOccurrence(array, value) {
    var count = 0;
    array.forEach((v) => (v === value && count++));
    return count;
}

console.log(getOccurrence(arr, 1));  // 2
console.log(getOccurrence(arr, 3));  // 3

number of repetition in an array javascript

let targetted_array = [3,4,3,23,452,5,3,3,21,1,5,5];  

function countInArray(array, element) {
    let repeat_count = 0;
    for (let i = 0; i < array.length; i++) {
        if (array[i] === element) {
            repeat_count++;
        }
    }
    return repeat_count;
}

countInArray(targetted_array, 3) // will return 4. cuz "3" was repeated 4 times in the targetted_array
countInArray(targetted_array, 5) // will return 3. cuz "5" was repeated 3 times in the targetted_array

js find duplicates in array and count of numbers

const arr = ["a", "b", "c", "d", "e", "a", "b", "c", "f", "g", "h", "h", "h", "e", "a"]
const counts = {};
arr.forEach((x) => {
  counts[x] = (counts[x] || 0) + 1;
});
console.log(counts)

counting duplicate values javascript

var counts = {};
your_array.forEach(function(x) { counts[x] = (counts[x] || 0)+1; });

how to count duplicates in an array javascript

arr.reduce((b,c)=>((b[b.findIndex(d=>d.el===c)]||b[b.push({el:c,count:0})-1]).count++,b),[]);