大家好我在这三种方法中有三个javascript文件（mongomart.js，items.js和cart.js）mongomart.js是驱动方法，其中包含配置和所有其他东西。当我运行“node mongomart.js “跟随错误来了。
ReferenceError: db is not defined
at ItemDAO.getCategories (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\items.js:48:14)
at C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\mongomart.js:72:15
at Layer.handle [as handle_request] (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\layer.js:95:5)
at next (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\route.js:131:13)
at Route.dispatch (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\route.js:112:3)
at Layer.handle [as handle_request] (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\layer.js:95:5)
at C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\index.js:277:22
at Function.process_params (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\index.js:330:12)
at next (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\index.js:271:10)
at Function.handle (C:\Users\Lalit\Desktop\final_project.9265ac2868d2\lab_0\mongomart\mongomart\node_modules\express\lib\router\index.js:176:3)
Here is all Js files
mongomart.js
var express = require('express'),
bodyParser = require('body-parser'),
nunjucks = require('nunjucks'),
MongoClient = require('mongodb').MongoClient,
assert = require('assert'),
ItemDAO = require('./items').ItemDAO,
CartDAO = require('./cart').CartDAO;
// Set up express
app = express();
app.set('view engine', 'html');
app.set('views', __dirname + '/views');
app.use('/static', express.static(__dirname + '/static'));
app.use(bodyParser.urlencoded({ extended: true }));
var env = nunjucks.configure('views', {
autoescape: true,
express: app
});
var nunjucksDate = require('nunjucks-date');
nunjucksDate.setDefaultFormat('MMMM Do YYYY, h:mm:ss a');
env.addFilter("date", nunjucksDate);
var ITEMS_PER_PAGE = 5;
// Hardcoded USERID for use with the shopping cart portion
var USERID = "558098a65133816958968d88";
MongoClient.connect('mongodb://localhost:27017/mongomart', function(err, db) {
"use strict";
assert.equal(null, err);
console.log("Successfully connected to MongoDB.");
var items = new ItemDAO(db);
var cart = new CartDAO(db);
var router = express.Router();
// Homepage
router.get("/", function(req, res) {
"use strict";
var page = req.query.page ? parseInt(req.query.page) : 0;
var category = req.query.category ? req.query.category : "All";
items.getCategories(function(categories) {
items.getItems(category, page, ITEMS_PER_PAGE, function(pageItems) {
items.getNumItems(category, function(itemCount) {
var numPages = 0;
if (itemCount > ITEMS_PER_PAGE) {
numPages = Math.ceil(itemCount / ITEMS_PER_PAGE);
}
res.render('home', { category_param: category,
categories: categories,
useRangeBasedPagination: false,
itemCount: itemCount,
pages: numPages,
page: page,
items: pageItems });
});
});
});
});
router.get("/search", function(req, res) {
"use strict";
var page = req.query.page ? parseInt(req.query.page) : 0;
var query = req.query.query ? req.query.query : "";
items.searchItems(query, page, ITEMS_PER_PAGE, function(searchItems) {
items.getNumSearchItems(query, function(itemCount) {
var numPages = 0;
if (itemCount > ITEMS_PER_PAGE) {
numPages = Math.ceil(itemCount / ITEMS_PER_PAGE);
}
res.render('search', { queryString: query,
itemCount: itemCount,
pages: numPages,
page: page,
items: searchItems });
});
});
});
router.get("/item/:itemId", function(req, res) {
"use strict";
var itemId = parseInt(req.params.itemId);
items.getItem(itemId, function(item) {
console.log(item);
if (item == null) {
res.status(404).send("Item not found.");
return;
}
var stars = 0;
var numReviews = 0;
var reviews = [];
if ("reviews" in item) {
numReviews = item.reviews.length;
for (var i=0; i<numReviews; i++) {
var review = item.reviews[i];
stars += review.stars;
}
if (numReviews > 0) {
stars = stars / numReviews;
reviews = item.reviews;
}
}
items.getRelatedItems(function(relatedItems) {
console.log(relatedItems);
res.render("item",
{
userId: USERID,
item: item,
stars: stars,
reviews: reviews,
numReviews: numReviews,
relatedItems: relatedItems
});
});
});
});
router.post("/item/:itemId/reviews", function(req, res) {
"use strict";
var itemId = parseInt(req.params.itemId);
var review = req.body.review;
var name = req.body.name;
var stars = parseInt(req.body.stars);
items.addReview(itemId, review, name, stars, function(itemDoc) {
res.redirect("/item/" + itemId);
});
});
/*
*
* Since we are not maintaining user sessions in this application, any interactions with
* the cart will be based on a single cart associated with the the USERID constant we have
* defined above.
*
*/
router.get("/cart", function(req, res) {
res.redirect("/user/" + USERID + "/cart");
});
router.get("/user/:userId/cart", function(req, res) {
"use strict";
var userId = parseInt(req.params.userId);
cart.getCart(userId, function(userCart) {
var total = cartTotal(userCart);
res.render("cart",
{
userId: userId,
updated: false,
cart: userCart,
total: total
});
});
});
router.post("/user/:userId/cart/items/:itemId", function(req, res) {
"use strict";
var userId = parseInt(req.params.userId);
var itemId = parseInt(req.params.itemId);
var renderCart = function(userCart) {
var total = cartTotal(userCart);
res.render("cart",
{
userId: userId,
updated: true,
cart: userCart,
total: total
});
};
cart.itemInCart(userId, itemId, function(item) {
if (item == null) {
items.getItem(itemId, function(item) {
item.quantity = 1;
cart.addItem(userId, item, function(userCart) {
renderCart(userCart);
});
});
} else {
cart.updateQuantity(userId, itemId, item.quantity+1, function(userCart) {
renderCart(userCart);
});
}
});
});
router.post("/user/:userId/cart/items/:itemId/quantity", function(req, res) {
"use strict";
var userId = parseInt(req.params.userId);
var itemId = parseInt(req.params.itemId);
var quantity = parseInt(req.body.quantity);
cart.updateQuantity(userId, itemId, quantity, function(userCart) {
var total = cartTotal(userCart);
res.render("cart",
{
userId: userId,
updated: true,
cart: userCart,
total: total
});
});
});
function cartTotal(userCart) {
"use strict";
var total = 0;
for (var i=0; i<userCart.items.length; i++) {
var item = userCart.items[i];
total += item.price * item.quantity;
}
return total;
}
// Use the router routes in our application
app.use('/', router);
// Start the server listening
var server = app.listen(3000, function() {
var port = server.address().port;
console.log('Mongomart server listening on port %s.', port);
});
});
**items.js**
var MongoClient = require('mongodb').MongoClient,
assert = require('assert');
function ItemDAO(database) {
"use strict";
this.db = database;
this.getCategories = function(callback) {
"use strict";
/*
* TODO-lab1A
*
* LAB #1A:
* Create an aggregation query to return the total number of items in each category. The
* documents in the array output by your aggregation should contain fields for
* "_id" and "num". HINT: Test your mongodb query in the shell first before implementing
* it in JavaScript.
*
* Ensure categories are organized in alphabetical order before passing to the callback.
*
* Include a document for category "All" in the categories to pass to the callback. All
* should identify the total number of documents across all categories.
*
*/
var categories = [];
var category =
db.collection('item').aggregate([{$group: {_id: "$category", num: {$sum: 1}}},{$sort:{_id:1}}]);
错误出现在上面一行
categories.push(category)
// TODO-lab1A Replace all code above (in this method).
callback(categories);
}
this.getItems = function(category, page, itemsPerPage, callback) {
"use strict";
/*
* TODO-lab1B
*
* LAB #1B:
* Create a query to select only the items that should be displayed for a particular
* page. For example, on the first page, only the first itemsPerPage should be displayed.
* Use limit() and skip() and the method parameters: page and itemsPerPage to identify
* the appropriate products. Pass these items to the callback function.
*
* Do NOT sort items.
*
*/
var pageItem = this.createDummyItem();
var pageItems = [];
for (var i=0; i<5; i++) {
pageItems.push(pageItem);
}
// TODO-lab1B Replace all code above (in this method).
callback(pageItems);
}
this.getNumItems = function(category, callback) {
"use strict";
var numItems = 0;
/*
* TODO-lab1C
*
* LAB #1C: Write a query that determines the number of items in a category and pass the
* count to the callback function. The count is used in the mongomart application for
* pagination. The category is passed as a parameter to this method.
*
* See the route handler for the root path (i.e. "/") for an example of a call to the
* getNumItems() method.
*
*/
callback(numItems);
}
this.searchItems = function(query, page, itemsPerPage, callback) {
"use strict";
/*
* TODO-lab2A
*
* LAB #2A: Using the value of the query parameter passed to this method, perform
* a text search against the item collection. Do not sort the results. Select only
* the items that should be displayed for a particular page. For example, on the
* first page, only the first itemsPerPage matching the query should be displayed.
* Use limit() and skip() and the method parameters: page and itemsPerPage to
* select the appropriate matching products. Pass these items to the callback
* function.
*
* You will need to create a single text index on title, slogan, and description.
*
*/
var item = this.createDummyItem();
var items = [];
for (var i=0; i<5; i++) {
items.push(item);
}
// TODO-lab2A Replace all code above (in this method).
callback(items);
}
this.getNumSearchItems = function(query, callback) {
"use strict";
var numItems = 0;
/*
* TODO-lab2B
*
* LAB #2B: Using the value of the query parameter passed to this method, count the
* number of items in the "item" collection matching a text search. Pass the count
* to the callback function.
*
*/
callback(numItems);
}
this.getItem = function(itemId, callback) {
"use strict";
/*
* TODO-lab3
*
* LAB #3: Query the "item" collection by _id and pass the matching item
* to the callback function.
*
*/
var item = this.createDummyItem();
// TODO-lab3 Replace all code above (in this method).
callback(item);
}
this.getRelatedItems = function(callback) {
"use strict";
this.db.collection("item").find({})
.limit(4)
.toArray(function(err, relatedItems) {
assert.equal(null, err);
callback(relatedItems);
});
};
this.addReview = function(itemId, comment, name, stars, callback) {
"use strict";
/*
* TODO-lab4
*
* LAB #4: Add a review to an item document. Reviews are stored as an
* array value for the key "reviews". Each review has the fields: "name", "comment",
* "stars", and "date".
*
*/
var reviewDoc = {
name: name,
comment: comment,
stars: stars,
date: Date.now()
}
var dummyItem = this.createDummyItem();
dummyItem.reviews = [reviewDoc];
callback(dummyItem);
}
this.createDummyItem = function() {
"use strict";
var item = {
_id: 1,
title: "Gray Hooded Sweatshirt",
description: "The top hooded sweatshirt we offer",
slogan: "Made of 100% cotton",
stars: 0,
category: "Apparel",
img_url: "/img/products/hoodie.jpg",
price: 29.99,
reviews: []
};
return item;
}
}
module.exports.ItemDAO = ItemDAO;
答案 0 :(得分：0)
正如您在代码中看到的那样：
this.getRelatedItems = function(callback) {
"use strict";
this.db.collection("item").find({})
.limit(4)
.toArray(function(err, relatedItems) {
assert.equal(null, err);
callback(relatedItems);
});
};
您需要将集合指定为参数：
this.db.collection("item").