javascript - TypeError : Cannot read property 'then' of undefined. 当我尝试运行 updatefirst 函数时出现此错误

Question

我正在尝试运行 updatefirst 函数，但即使我将预定义值传递给 get_plo_amount 中的解析函数，也会一次又一次出现相同的错误。console.log(result) 行运行表明没有问题获取数据。我不知道我在这里做错了什么:(。任何帮助将不胜感激。谢谢。

const get_plo_amount = function(p){
    plo.findOne({phone : p}).then((result) => {
        console.log(result) //this line is running
        return new Promise((resolve,reject) => {
            resolve(result.daily_amount)
        })

    }).catch((e) => {
        console.log("catch")
        return new Promise((resolve,reject) => {
            reject(e)
        })
    })

}

//updatefirst
const updatefirst = function(plo,date){
    driver.find({associated_plo : plo}).then((result) => {
        //console.log(result)//delete this
        get_plo_amount(plo).then((amount) => {
            console.log(amount)
            var arr
            for(i=0;i<result.length;i++){
                var pdue = parseInt(result[i].balance) + amount
                var d_obj = {
                    driver : result[i].name,
                    phone : result[i].phone,
                    auto_number : result[i].auto_number,
                    amount : pdue,
                }
             //   console.log(d_obj)//delete this
                arr[i] = d_obj
            }

            const obj = {
                associated_plo : plo,
                date : date,
                earning : "0",
                payments : arr
            }
            const t = new transactions(obj)

            t.save().then(() => {
                return "success"
            }).catch((e) => {
                return e
            })

        }).catch((e) => {
            console.log(e)
            return e
        })


    }).catch((e) => {
        console.log(e)
        return e
    })
}

Answer 1

您应该返回一个 promise ，以使 then() 方法起作用。尝试像这样更新你的函数:

const get_plo_amount = function(p){
    return plo.findOne({phone : p}).then((result) => {
        console.log(result) //this line is running
        return new Promise((resolve,reject) => {
            resolve(result.daily_amount)
        })

    }).catch((e) => {
        console.log("catch")
        return new Promise((resolve,reject) => {
            reject(e)
        })
    })

}