count a element in any array code example

Example 1: Count frequency of array elements js

var arr = [5, 5, 5, 2, 2, 2, 2, 2, 9, 4]

const map = arr.reduce((acc, e) => acc.set(e, (acc.get(e) || 0) + 1), new Map());

console.info([...map.keys()]) // to get unique elements
console.info([...map.values()]) // to get the occurrences
console.info([...map.entries()]) // to get the pairs [element, frequency]

Example 2: Number of array elements

A = magic(4);
A(:,:,2) = A'
n = numel(A)