错误返回数据foreach查找mongodb数组答案

【问题标题】：error returning data foreach find mongodb array错误返回数据foreach查找mongodb数组
【发布时间】：2020-09-12 17:56:00
【问题描述】：

我正在查阅一份文件，结果我查阅了另一份文件model，但最后，什么都没有返回给我，foreach 不等待await。

ShoppingCart.find({
   "userId": id
}).then(async ShoppingCart => {
   let distinctTypes = ShoppingCart[0].productsCart;
   distinctTypes.sort(function(r, u) {
      return r.manufacturerId > u.manufacturerId ? 1 : r.manufacturerId < u.manufacturerId ? -1 : 0
   });
   let products = [];
   let data2 = await distinctTypes.forEach(async function(thisType) {
      let id = thisType.productId;
      let data = await Product.findById(id).then(Product => {
         thisType.productId = Product;
         products.push(thisType);
         return products;
      });
      return data; ///at this point the information is correct
   });
   return data2;
});

“数据”：空

【问题讨论】：

标签： javascript node.js mongodb mongoose async-await

【解决方案1】：

发生这种情况是因为 forEach 没有以同步方式执行。请改用 For of 循环。

详细回答：- Using async/await with a forEach loop

【讨论】：

非常好的 await 答案（distinctTypes 的常量产品）{}

【解决方案2】：

Array.prototype.forEach 不等待是正确的。相反，您应该使用Array.prototype.map 和Promise.all

ShoppingCart.find({
   "userId": id
}).then(async cart => {
   let distinctTypes = cart[0].productsCart;
   distinctTypes.sort(function(r, u) {
      return r.manufacturerId > u.manufacturerId ? 1 : r.manufacturerId < u.manufacturerId ? -1 : 0
   });
   const distinctTypesWithProducts = await Promise.all(
     distinctTypes.map(async function(thisType) {
        let id = thisType.productId;
        const product = await Product.findById(id)
        thisType.product = product // changed assignment of product to thisType.product
        return thisType
     });
   );
   return distinctTypesWithProducts;
});

您可以使用我开始的project 简化上述内容。欢迎投稿。

const { pipe, assign, map, get } = require('rubico')

// userId => cart
const findCartByUserID = userId => ShoppingCart.find({ userId })

// [distinctType] => [distinctType] sorted
const sortDistinctTypes = distinctTypes => distinctTypes.sort((r, u) => {
  return r.manufacturerId > u.manufacturerId ? 1 : r.manufacturerId < u.manufacturerId ? -1 : 0
})

// distinctType => distinctTypeWithProduct
const assignProduct = assign({
  product: pipe([
    get('productId'), // distinctType => productId
    Product.findById, // productId => product
  ]), // distinctType.product = product; return distinctType
})

// userId => [distinctTypeWithProduct, distinctTypeWithProduct, ...]
const getDistinctTypesWithProductFromUserID = pipe([
  findCartByUserID,
  // userId => cart

  get([0, 'productsCart']),
  // cart => distinctTypes

  sortDistinctTypes,
  // distinctTypes => sortedDistinctTypes

  map(assignProduct),
  // sortedDistinctTypes => [distinctTypeWithProduct, distinctTypeWithProduct, ...]
])

getDistinctTypesWithProductFromUserID(id)

【讨论】：