let wh = [{"hours":"no"},{"hours": "09:00-17:00"},{"hours": "09:00-17:00"},{"hours": "09:00-17:00"},{"hours": "09:00-17:00"},{"hours": "09:00-17:00"},{"hours":"no"}];
let fwh = [];
for(let i = 0; i < wh.length; i++){
    let h = wh[i].hours;
    let found = false;
    for(let j = 0; j < fwh.length; j++){
        if(fwh[j].hours === wh[i].hours){
            found = true;
            fwh[j].days.push(i);
        }
    }
    if(!found){
        fwh.push({days:[i], hours:wh[i].hours});
    }
}
console.log(fwh);