findOneAndUpdate 增量而不是猫鼬中的更新

问题描述：

我有一个函数可以增加或减少信用.但我下面的代码只是替换信用值.猫鼬有什么捷径可以增加或减少吗?否则我将不得不获取值然后将其插入，我认为这不是这样做的方法.

I have a function that suppose to add up or decrease credit. But my below code merely replace the credit value. Is there any shortcut in mongoose that I can do increment or decrement? else I will have to get the value then insert it back, which I think is not the way to do it.

function update_total_credit(total_amount, topup_value){
            User.findOneAndUpdate(
                {email: user_email}, 
                {$set:{credit:total_amount}}, 
                {new: true}, 
                function(err, response){
                if(err){
                    res.json(0);
                }else{
                    res.json(response.credit);
                }
            });

        }

答

可以动态设置值并在查询中传递

You can set the value dynamic and pass it in the query

function update_total_credit(total_amount, topup_value) {
//The flag value means your breakpoint where you decide which value should go in query, you can change on your requirement basis
  var flag = 1;//increament by 1 every time
  if (!flag)
    flag = -1;//decreament by 1 every time
  User.findOneAndUpdate({
      email: user_email
    }, {
      $inc: {
        credit: flag
      }
    },
    function(err, response) {
      if (err) {
        res.json(0);
      } else {
        res.json(response.credit);
      }
    });
}

请参阅此处的参考 $inc

findOneAndUpdate 增量而不是猫鼬中的更新

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