Node Js中的For循环后返回响应？答案

【问题标题】：Return Response After For loop in Node Js?Node Js中的For循环后返回响应？
【发布时间】：2021-10-27 03:23:15
【问题描述】：

我正在尝试从我的数据库中获取用户，然后遍历它们并在外部服务器中获取每个用户余额，该服务器以每个用户的余额进行响应。我过滤响应并将我需要的数据推送到一个数组中。最后我应该将此数组发送到客户端。下面的代码将说明这一点

app.get("/usersData", (req, res) => {

  var data = [];
  Users.find({}).then((users) => {
    users.forEach((user) => {
      var body = [];
      var userObj = { userName: user.userName, assets: [] };
      //Call external Server To get User assets amount
      ExternalServer.GetAssetsOfUser(user.secretKey).then((assets) => {
        var assetsArr = [];
  
        //Loop through the assets and get the one with greater than 50 and check for the price
        for (const asset in assets) {
          if (asset.amount > 50) {
            //Call the server again to get price assets
            ExternalServer.GetPriceOfAsset(asset.name).then((price) => {
              assetsArr.push({
                name: asset.name,
                value: +parseFloat(asset.amount).toFixed(4) * price,
              });
            });
          }
        }
      });
      //Add assetsArr to user Assets
      userObj.assets = assetsArr;
      body.push(userObj);
    });
    res.send(body);
  });




})

当我调试代码时，我发现我总是发送带有空数组的响应，甚至在进入其余代码之前。我想在获取所有数据后发送响应

【问题讨论】：

标签： node.js express http response

【解决方案1】：

我可以看到一些问题：

您在 users.forEach() 循环中定义 var body = [];
在终止 res.send() 之前，您无需等待 ExternalServer.GetPriceOfAsset() 或 ExternalServer.GetAssetsOfUser() 调用来解决他们的承诺。
您根本没有处理任何错误，尽管我没有在下面的代码中添加任何内容来解决这个问题。

我认为解决方案类似于以下内容，尽管我们当然不能自己运行它来确定。

app.get("/usersData", (req, res) => {
  Users.find({}).then(async (users) => {
    // Move this outside of loop
    const body = [];
    // Using "for" iterator instead of improper async forEach
    for ( let i = 0; i < users.length; i++ ) {
      const user = users[i];
      const userObj = { userName: user.userName, assets: [] };
      //Call external Server To get User assets amount
      const assets = await ExternalServer.GetAssetsOfUser(user.secretKey);
      const assetsArr = [];

      //Loop through the assets and get the one with greater than 50 and check for the price
      for (const asset in assets) {
        if (asset.amount > 50) {
          //Call the server again to get price assets
          const price = await ExternalServer.GetPriceOfAsset(asset.name);
          assetsArr.push({
            name: asset.name,
            value: +parseFloat(asset.amount).toFixed(4) * price,
          });
        }
      }
      //Add assetsArr to user Assets
      userObj.assets = assetsArr;
      body.push(userObj);
    });
    res.send(body);
  });
});

【讨论】：