var bmi = (weight / (height*height));

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');

}