如何修改金额增减函数，使其递增上限设置为120？

只需修改incrementAmount函数中的上限判断条件，将原来的最大值2替换为120即可，递减函数的逻辑无需改动（下限仍保持1）。

修改后的完整代码如下：

const decrementAmount = () => {
   let newAmount = Amount - 1;
   if (newAmount < 1) {
     newAmount = 1;
   }
   setAmount(newAmount);
 };

 const incrementAmount = () => {
   let newAmount = Amount + 1;
   if (newAmount > 120) {
     newAmount = 120;
   }
   setAmount(newAmount);
 };

如果后续可能需要调整上下限值，建议把常量抽离出来，让代码更易维护：

const MIN_AMOUNT = 1;
const MAX_AMOUNT = 120;

const decrementAmount = () => {
   let newAmount = Amount - 1;
   if (newAmount < MIN_AMOUNT) {
     newAmount = MIN_AMOUNT;
   }
   setAmount(newAmount);
 };

 const incrementAmount = () => {
   let newAmount = Amount + 1;
   if (newAmount > MAX_AMOUNT) {
     newAmount = MAX_AMOUNT;
   }
   setAmount(newAmount);
 };

内容的提问来源于stack exchange，提问作者Van Duo