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
let a = [1, 2, 3, 4, 2, 2, 4, 1, 5, 6]
let b = [...new Set(a.sort().filter((o, i) => o !== undefined && a[i + 1] !== undefined && o === a[i + 1]))]
Example 3: check for duplicates in array javascript
[1, 2, 3].every((e, i, a) => a.indexOf(e) === i)
[1, 2, 1].every((e, i, a) => a.indexOf(e) === i)
Example 4: find duplicate values in array javascript
const findDuplicates = (arr) => {
let sorted_arr = arr.slice().sort();
let results = [];
for (let i = 0; i < sorted_arr.length - 1; i++) {
if (sorted_arr[i + 1] == sorted_arr[i]) {
results.push(sorted_arr[i]);
}
}
return results;
}
let duplicatedArray = [9, 4, 111, 2, 3, 9, 4, 5, 7];
console.log(`The duplicates in ${duplicatedArray} are ${findDuplicates(duplicatedArray)}`);
Example 5: check for duplicates in array javascript
[1, 2, 2, 4, 3, 4].filter((e, i, a) => a.indexOf(e) !== i)