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)