Example 1: count duplicates array js
uniqueCount = ["a","b","c","d","d","e","a","b","c","f","g","h","h","h","e","a"];
var count = {};
uniqueCount.forEach(function(i) { count[i] = (count[i]||0) + 1;});
console.log(count);
Example 2: how to get duplicate values from array in javascript
var array = [1, 2, 2, 3, 3, 4, 5, 6, 2, 3, 7, 8, 5, 22, 1, 2, 511, 12, 50, 22];
console.log([...new Set(
array.filter((value, index, self) => self.indexOf(value) !== index))]
);
Example 3: how to get duplicate values from array in javascript
const arr = ["q", "w", "w", "e", "i", "u", "r"]
arr.reduce((acc, cur) => {
if(acc[cur]) {
acc.duplicates.push(cur)
} else {
acc[cur] = true
}
}, { duplicates: [] })