promise mongoose 循环遍历查询

Question

let result = []; //存放查询结果model.WithdrawModel.find({status:'processing'}, (err, doc) => {            if (err) {                console.log(err);                res.json({ code: -1, msg: '查询失败'});                return;            } else {                doc.map((item) => {                    model.UserModel.findOne({phone:item.phone},'name IDcard bank bankCard bank_area bank_name', (err, bankInfo) => {                        if (err) {                            console.log(err);                        } else {                            let obj = {};                            Object.assign(obj, JSON.parse(JSON.stringify(item)), JSON.parse(JSON.stringify(bankInfo)));                            result.push(obj);                            console.log(result);                         }                    })                });                res.json({ code: 0, msg: '查询成功', result: result});                return;  } });循环遍历查询，上述 result 直接返回空值，请问怎么保证 doc.map 内部的查询都结束之后再取出 result 的值？

Answer 1

promise.all 实现如下：

        let result = []; //存放查询结果
        let doc1 = []; //存放第一次查询的结果
        model.WithdrawModel.find({status:'processing'}).exec().then((doc) => {
            doc1 = doc;
            const promises = doc.map(item => model.UserModel.findOne({phone:item.phone},'name IDcard bank bankCard bank_area bank_name'));
            return Promise.all(promises);
        })
        .then((bankInfoList) => {//promise.all返回的结果是一一对应的
            for(let i=0; i<doc1.length; i++){
                let obj = {};
               
                Object.assign(obj, JSON.parse(JSON.stringify(doc1[i])), JSON.parse(JSON.stringify(bankInfoList[i])));
                result.push(obj);
            }
            return new Promise((resolve, reject) => {
                    resolve(result);
            })          
        })
        .then((result) => {
            return new Promise(() => {
                res.json({ code: 0, msg: '查询成功', result: result});
                return;
            });
        })
        .catch((e) => {
            console.log(e);
            res.json({ code: -1, msg: '查询失败'});
            return;
        });