hhmmssToMillis(hhmmss) {
   let time= hhmmss.split(':').reverse();
   let millis = 0;
   switch(time.length) {
     case 1:
         millis = parseInt(time[0]) * 1000;
         break;
     case 2:
         millis = (parseInt(time[1]) * 60 + parseInt(time[0])) * 1000;
         break;
     case 3:
         millis = (parseInt(time[2]) * 60 * 60 + parseInt(time[1]) * 60 + parseInt(time[0])) * 1000;
         break;
   }
   return millis;
}

let time= hhmmss.split(':').reverse();
return time.reduce((millis, current, index) => {
   return millis + parseInt(current) * 60 ** index;
}, 0) * 1000;

hhmmssToMillis(hhmmss) {
    const time = hhmmss.split(':').reverse();
    switch(time.length) {
       case 1:
         return parseInt(time[0]) * 1000;
       case 2:
         return (parseInt(time[1]) * 60 + parseInt(time[0])) * 1000;
       case 3:
         return (parseInt(time[2]) * 60 * 60 + parseInt(time[1]) * 60 + parseInt(time[0])) * 1000;
    }
    return 0;
}