Node.服务器瀑布错误类型错误：无法读取未定义的属性'Symbol(Symbol.toStringTag)'

Question

我正在编写具有两个功能的服务器，一个使用另一个函数的输出。当服务器运行时，它会产生错误：

TypeError: Cannot read property 'Symbol(Symbol.toStringTag)' of undefined
    at isAsync (/Users/charles/Documents/Router/node_modules/async/dist/async.js:228:32)
    at wrapAsync (/Users/charles/Documents/Router/node_modules/async/dist/async.js:232:12)
    at nextTask (/Users/charles/Documents/Router/node_modules/async/dist/async.js:5308:20)
    at Object.waterfall (/Users/charles/Documents/Router/node_modules/async/dist/async.js:5320:5)
    at /Users/charles/Documents/Router/routes/yelp.js:46:15
    at /Users/charles/Documents/Router/node_modules/mongojs/lib/cursor.js:59:24
    at handleCallback (/Users/charles/Documents/Router/node_modules/mongojs/node_modules/mongodb/lib/utils.js:120:56)
    at /Users/charles/Documents/Router/node_modules/mongojs/node_modules/mongodb/lib/cursor.js:683:5
    at handleCallback (/Users/charles/Documents/Router/node_modules/mongojs/node_modules/mongodb-core/lib/cursor.js:171:5)
    at setCursorDeadAndNotified (/Users/charles/Documents/Router/node_modules/mongojs/node_modules/mongodb-core/lib/cursor.js:505:3)

代码是

const express = require('express');
const router = express.Router();
const request = require('request-promise-lite');
const async = require('async');
router.get('/yelp', function(req, res, next) {
  db.input.find({}, {
      term: 1,
      location: 1,
      _id: 0
    })
    .limit(1).sort({
      $natural: -1
    }, function(err, input) {
      if (err) {
        res.send(err)
      }
      console.log(input);
      async.waterfall([yelpSearch(input[0]), googleSearch],
        function sendJson(err, restaurants) {
          console.log("waterfall starting");
          if (err) res.send(err);
          res.json(restaurants);
        })
    })
});
// Yelp API call
const yelpSearch = function(input, cb) {
  const client = yelp.client(apiKey);
  client.search(input)
    .then(response => {
      console.log(response.jsonBody.businesses);
      cb(null, response.jsonBody.businesses);
    })
    .catch(e => {
      console.log(e);
    });
}
// Google API call
const googleSearch = function(restaurants, cb) {
  console.log("google starts")
  var apiKey = google_apiKey;
  var cseKey = cseID;
  restaurants.forEach(function(restaurant) {
    var keyWord = restaurant.name + restaurant.city + restaurant.state;
    var googleURL = "https://www.googleapis.com/customsearch/v1?key=" + apiKey +
      "q=" + keyWord +
      "&searchType=image" +
      "&cx" + cseKey +
      "&count=5" +
      "&safe=medium";
    var imageURLs = [];
    request.get(googleURL, {
      json: true,
      headers: {
        'User-Agent': 'thaorell'
      }
    }).then(function(response) {
      response.items.forEach(function(item) {
        imageURLs.append(item.link)
      });
      restaurant.append(imageURLs);
      console.log(imageURLs);
    })
  })
  cb(null, restaurants)
};

有人在这方面有任何经验吗？错误与以下方式存在：async.waterfall([yelpSearch(input[0]), googleSearch]。我正在使用Yelp API搜索餐厅，然后为每家餐厅寻找餐厅，我想从Google搜索该餐厅的图像。

Answer 1

我猜，您正在错误地将参数传递给瀑布中的第一个功能，应该是：

async.waterfall([
    async.constant(input[0]),
    yelpSearch,
    googleSearch
], function sendJson(err, restaurants) {
    // ...
});

Answer 2

yelpSearch和 googleSearch均为 const s;他们没有升起。因此，在调用async.waterfall([yelpSearch(input[0]), googleSearch],时，函数尚不存在，因此失败。将它们声明在router.get上方(或将其更改为引起的函数声明(。