var bmi = weight / (height * height);

if (bmi <= 18.5) 

        {console.log('过轻')}

else if (bmi <= 25)

        {console.log('过轻')}

else if (bmi <= 28)

        {console.log('过重')}

else if (bmi <= 32)

        {console.log('肥胖')}

else

        {console.log('严重肥胖')}