res.query 错误中的默认值

Question

我想为 res.query 参数设置默认值，这意味着 api 不需要来自客户端的参数。因此我想回退到默认值。这是我回复请求的方法：

  exports.all = (req, res, next) => {
    const filterParam = req.query.filterBy;
    const loc = req.query.loc;
    let whereCondition = {isPublic: true};
    let findCondition = {};
    let pageOptions = {
      skip: req.query.skip || 0,
      limit: req.query.limit || 10
    };

    if (filterParam == 'building') {
      whereCondition.type = 'building'
    } else if (filterParam == 'center') {
      whereCondition.type = 'center';
    } else if (filterParam == 'geo') {
      const distanceInKm = 125 / 111.2;
      findCondition.loc = { $near: [loc[1], loc[0]], $maxDistance: distanceInKm }
    }

    building
      .find(findCondition)
      .skip(pageOptions.skip)
      .limit(pageOptions.limit)
      .where(whereCondition)
      .exec((err, buildings) => {
        if (err) { res.status(400).json({error: err.data}); }

        return res.status(200).json({buildings: buildings});
      });
  };

错误

  GET /api/building/all?limit=4&skip=4 200 13.758 ms - 2
  events.js:160
        throw er; // Unhandled 'error' event
        ^

  Error: Can't set headers after they are sent.
      at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:356:11)
      at ServerResponse.header (/path/to/project/server/node_modules/express/lib/response.js:718:10)
      at ServerResponse.send (/path/to/project/server/node_modules/express/lib/response.js:163:12)
      at ServerResponse.json (/path/to/project/server/node_modules/express/lib/response.js:249:15)
      at Building.find.skip.limit.where.exec (/path/to/project/server/controllers/BuildingCtrl.js:197:30)
      at /path/to/project/server/node_modules/mongoose/lib/query.js:2260:9
      at process._tickCallback (internal/process/next_tick.js:103:7)

Answer 1

您需要在if 条件中添加return 语句。我认为 mongoose 查询有问题，它 returns 一个错误：

...
.exec((err, buildings) => {
  if (err) {
    return res.status(400).json({error: err.data});
  }
  res.send({buildings: buildings});
});

顺便说一句，express 默认设置 200 个状态，send 方法根据响应数据设置 content-type。

res.query 错误中的默认值

default values in res.query error

response

node.js

express

错误