function duplicates(arr) { var arrs = [] for(var i of arr){ arrs.indexOf(i) === -1 && arr.indexOf(i) !== arr.lastIndexOf(i) && arrs.push(i) } return arrs }
function duplicates(arr) { let newarr= [] for(let i = 0;i<arr.length;i++){ for(let j = i+1;j<arr.length;j++){ if(arr[i] == arr[j]){ arr.splice(j,1) newarr.push(arr[i]) break } } } return newarr }
function duplicates(arr) { let newarr= [] for(let i = 0;i<arr.length;i++){ for(let j = i+1;j<arr.length;j++){ if(arr[i] == arr[j]){ arr.splice(j,1) newarr.push(arr[i]) break } } } return newarr }
function duplicates(arr) { var s = new Set() var a = new Set() for(var i in arr){ var len = s.size s.add(arr[i]) if(s.size == len){ a.add(arr[i]) } } return [...a] }
function duplicates(arr) { let repeat = []; let obj = {} arr.forEach(val => { obj[val] = obj[val] ? obj[val]+1 : 1 if(obj[val] === 2){ repeat.push(val) } }) return repeat }