微信开发者工具JS，为什么else if 条件不成立还是会进去

Question

let Unit
let CY =parseInt(bigNum.add(Cycleunit[0],-3),16)
//此时提取到的CY为9
let Cycleunit3

if(CY<4){
Unit ="分"
let Cycleunit1 = Cycleunit.join("")
let Cycleunit2 = bigNum.add(Cycleunit1,-33)
Cycleunit3 = parseInt(Cycleunit2,16)
}
else if(4<=CY<=7){
Unit ="时"
let Cycleunit1 = Cycleunit.join("")
let Cycleunit2 = bigNum.add(Cycleunit1,-73)
Cycleunit3 = parseInt(Cycleunit2,16)
}
else if(8<=CY<=11){
Unit ="日"
let Cycleunit1 = Cycleunit.join("")
let Cycleunit2 = bigNum.add(Cycleunit1,-"b3")
Cycleunit3 = parseInt(Cycleunit2,16)
}

Answer 1

else if(4<=CY<=7){ 不能这样写
else if(CY>=4 && CY<=7){