类型错误：无法读取未定义的属性“then”。 当我尝试运行 updatefirst 函数时出现此错误

Question

I am trying to run the updatefirst function but getting the same error again and again even when I pass a predefined value to the resolve function in get_plo_amount.The console.log(result) line runs which shows than there was no issue in fetching the data. I don't know what I am doing wrong here :( .Any help will be appreciated. Thanks .

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

You should return a promise, to make the then() method work. Try updating your function like this:

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)
        })
    })

}

Answer 2

2 more changes

1. you can return result.daily_amount without creating another promise
2. the promise in the catch is rejecting so you might as well remove the catch

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