new-set

let str="eefhhfjhfFfhwfhwr"
let arr=str.toLowerCase().split('')
// console.log(arr)
let filtered=arr.filter((e, i, a) => a.indexOf(e)!==i)
console.log('Filtered ',filtered)

let filtered1=arr.filter((e, i, a) => a.indexOf(e)===i)
console.log('All Letters Without Repeat, Using Filter: ', filtered1)

let res=[...new Set(arr)]
console.log('All Letters Without Repeat, Using new Set: ',res)

let result=[...new Set(filtered)]
console.log('Only Letters That Have Repeated:  ', result)