JSFiddle - React, Tailwind, and code Playground

by kpripper

JavaScript

var arr = [6, 4, 3, 3, 1, 5, 12, 4, 1, 2, 7, 2, 1];
 
var ks=[];
for(var value of arr){
	ks[value] = (ks[value]||0)+1;
}
var arr2 =[];
for(var i in arr) {
  if ( ks[ arr[i] ] > 1 ) {
		arr2.push(arr[i]);
		ks[ arr[i] ] = 0;
	}
}

console.log(arr2);