Question

如何从嵌套查询中返回值？我想将结果保存到全局变量。有人可以帮助我吗？

let result = null;

const returnMeal = () => {
  Dinner1300.count().exec(function (err, count) {

    const random = Math.floor(Math.random() * count)
  
    Dinner1300.findOne().skip(random).exec(
      function (err, result) {
        console.log(result)
      })
  })

Answer 1

您可以更改代码以使用Promise，或者只是传递一个回调以返回returnMeal并在那里处理响应

const returnMeal = clb => {
  Dinner1300.count().exec(function (err, count) {

    const random = Math.floor(Math.random() * count)

    Dinner1300.findOne().skip(random).exec(
      function (err, result) {
        clb(result)
      })
  })
}

returnMeal(result => {
  console.log(result);
  // move all your logic to handle the result here
})

Answer 2

只需将结果分配给全局声明的变量。

let result = null;

const returnMeal = () => {
  Dinner1300.count().exec(function (err, count) {

    const random = Math.floor(Math.random() * count)

    Dinner1300.findOne().skip(random).exec(
      function (err, result) {
        global.result = result;
        console.log(global.result)
      })
  })

Answer 3

使用module.exports

let result = null;

const returnMeal = () => {
  Dinner1300.count().exec(function (err, count) {
const random = Math.floor(Math.random() * count)

Dinner1300.findOne().skip(random).exec(
  function (err, res) {
    result = res;
    console.log(result);
  });
});

module.exports = result;

Answer 4

在函数中传递结果并在全局范围内设置值。

var globalScope = null;
Dinner1300.count().exec(function (err, count) {
    const random = Math.floor(Math.random() * count)
    Dinner1300.findOne().skip(random).exec(
        function (err, result) {
            setValue(result)
        })
})
function setValue(result) {
    globalScope = result;
}

将查询结果保存到全局变量

4 个答案: