Detect iOS device model name using JavaScript

function iOSdeviceDetection(){
 var ua = navigator.userAgent;

 if( /iPhone/.test(ua) ){
  if( screen.width*16 - screen.height*9 == 0 ) return 'iPhone 5';
  
  if( window.devicePixelRatio == 2 ){
   switch( getOSmajorver(ua) ){
    case 4:
     return 'iPhone 4';
    case 5:
    case 6:
     return 'iPhone 4 or 4S';
    default:
     return '?';
   }
  }

  switch( getOSmajorver(ua) ){
   case 1:
     return 'iPhone(1st)';
    case 2:
     return 'iPhone(1st) or 3G';
    case 3:
    case 4:
     return 'iPhone(1st), 3G or 3GS';
    case 5:
    case 6:
     return 'iPhone 3GS';
    default:
     return '?';
  }
 }

 if( /iPad/.test(ua) ){
  if( window.devicePixelRatio == 2 ){
   switch( getOSmajorver(ua) ){
    case 5:
     return 'iPad(3rd)';
    case 6:
     return 'iPhone(3rd) or (4th)';
    default:
     return '?';
   }
  }
  switch( getOSmajorver(ua) ){
   case 3:
    return 'iPad(1st)';
   case 4:
   case 5:
    return 'iPad(1st) or iPad 2';
   case 6:
    return 'iPad 2 or mini';
   default:
    return '?';
  }
 }

 if( /iPod/.test(ua) ){
  if( screen.width*16 - screen.height*9 == 0 )return 'iPod touch(5th)';
   
  if( window.devicePixelRatio == 2 ) return 'iPod touch(4th)';
  
  switch( getOSmajorver(ua) ){
   case 1:
    return 'iPod touch(1st)';
   case 2:
    return 'iPod touch(1st) or (2nd)';
   case 3:
    return 'iPod touch(1st), (2nd) or (3rd)';
   case 4:
    return 'iPod touch(2nd) or (3rd)';
   case 5:
    return 'iPod touch(3rd)';
   default:
    return '?';
  }
 }

 return 'not iOS device';

 function getOSmajorver( ua ){
  if( /OS 6/.test(ua) )return 6;
  if( /OS 5/.test(ua) )return 5;
  if( /OS 4/.test(ua) )return 4;
  if( /OS 3/.test(ua) )return 3;
  if( /OS 2/.test(ua) )return 2;
  return 1;
 }
}