function gemstones(arr) {
    
    // remove duplictions in each string 
        
        let strs = [];
        for(const i of arr){
            
                strs.push(i.split('').filter((a,index)=>i.indexOf(a)===index).join(''));
            
        }
        
 console.log(strs);
    let counts = {};
    for(const i of strs){
        for(const j of i){
            if(i.split('').includes(j))
            counts[j] = (counts[j]||0)+1;
        }
    }
    let counter = 0;
    for(const i in counts){
        if(counts[i]===arr.length){
            counter++;
        }
    }
   return (counter);
}