我正在用Node.js和mongoose写一个web应用程序。如何对我从.find()调用得到的结果进行分页?我想要一个功能可比的“限制50,100”在SQL。
当前回答
实现这一点的可靠方法是使用查询字符串从前端传递值。假设我们想要获得第2页,并将输出限制为25个结果。 page=2&limit=25 //这将被添加到您的URL: http:localhost:5000?= 2限制= 25页
让我们看看代码:
// We would receive the values with req.query.<<valueName>> => e.g. req.query.page
// Since it would be a String we need to convert it to a Number in order to do our
// necessary calculations. Let's do it using the parseInt() method and let's also provide some default values:
const page = parseInt(req.query.page, 10) || 1; // getting the 'page' value
const limit = parseInt(req.query.limit, 10) || 25; // getting the 'limit' value
const startIndex = (page - 1) * limit; // this is how we would calculate the start index aka the SKIP value
const endIndex = page * limit; // this is how we would calculate the end index
// We also need the 'total' and we can get it easily using the Mongoose built-in **countDocuments** method
const total = await <<modelName>>.countDocuments();
// skip() will return a certain number of results after a certain number of documents.
// limit() is used to specify the maximum number of results to be returned.
// Let's assume that both are set (if that's not the case, the default value will be used for)
query = query.skip(startIndex).limit(limit);
// Executing the query
const results = await query;
// Pagination result
// Let's now prepare an object for the frontend
const pagination = {};
// If the endIndex is smaller than the total number of documents, we have a next page
if (endIndex < total) {
pagination.next = {
page: page + 1,
limit
};
}
// If the startIndex is greater than 0, we have a previous page
if (startIndex > 0) {
pagination.prev = {
page: page - 1,
limit
};
}
// Implementing some final touches and making a successful response (Express.js)
const advancedResults = {
success: true,
count: results.length,
pagination,
data: results
}
// That's it. All we have to do now is send the `results` to the frontend.
res.status(200).json(advancedResults);
我建议将这个逻辑实现到中间件中,这样你就可以将它用于各种路由/控制器。
其他回答
以上回答是正确的。
只是一个插件,任何人谁是异步等待而不是 承诺! !
const findAllFoo = async (req, resp, next) => {
const pageSize = 10;
const currentPage = 1;
try {
const foos = await FooModel.find() // find all documents
.skip(pageSize * (currentPage - 1)) // we will not retrieve all records, but will skip first 'n' records
.limit(pageSize); // will limit/restrict the number of records to display
const numberOfFoos = await FooModel.countDocuments(); // count the number of records for that model
resp.setHeader('max-records', numberOfFoos);
resp.status(200).json(foos);
} catch (err) {
resp.status(500).json({
message: err
});
}
};
MongoDB官方博客有一个关于分页的条目,在那里他们解释了为什么“跳过”可能会很慢,并提供了替代方案:https://www.mongodb.com/blog/post/paging-with-the-bucket-pattern--part-1
下面的代码是为我工作良好。 你也可以在countDocs查询中添加查找过滤器和user same来获得准确的结果。
export const yourController = async (req, res) => {
const { body } = req;
var perPage = body.limit,
var page = Math.max(0, body.page);
yourModel
.find() // You Can Add Your Filters inside
.limit(perPage)
.skip(perPage * (page - 1))
.exec(function (err, dbRes) {
yourModel.count().exec(function (err, count) { // You Can Add Your Filters inside
res.send(
JSON.stringify({
Articles: dbRes,
page: page,
pages: count / perPage,
})
);
});
});
};
简单而强大的分页解决方案
async getNextDocs(no_of_docs_required: number = 5, last_doc_id?: string) {
let docs
if (!last_doc_id) {
// get first 5 docs
docs = await MySchema.find().sort({ _id: -1 }).limit(no_of_docs_required)
}
else {
// get next 5 docs according to that last document id
docs = await MySchema.find({_id: {$lt: last_doc_id}})
.sort({ _id: -1 }).limit(no_of_docs_required)
}
return docs
}
Last_doc_id:您获得的最后一个文档id
No_of_docs_required:你想要获取的文档数量,例如5、10、50等。
如果你不提供last_doc_id给方法,你会得到5个最新的文档 如果你提供了last_doc_id,那么你会得到下一个,即5个文档。
使用猫鼬,快递和翡翠的分页-这里有一个链接到我的博客与更多的细节
var perPage = 10
, page = Math.max(0, req.params.page)
Event.find()
.select('name')
.limit(perPage)
.skip(perPage * page)
.sort({
name: 'asc'
})
.exec(function(err, events) {
Event.count().exec(function(err, count) {
res.render('events', {
events: events,
page: page,
pages: count / perPage
})
})
})
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