var bmi = weight / height ** 2;

if (bmi < 18.5) {

    console.log('过轻');

} else if (bmi <= 25) {

    console.log('正常');

} else if (bmi <= 28) {

    console.log('过重');

} else if (bmi <= 32) {

    console.log('肥胖');

} else {

    console.log('严重肥胖');

}