Pagination in nodejs with mysql
You could try something like that (assuming you use Express 4.x).
Use GET parameters (here page is the number of page results you want, and npp is the number of results per page).
In this example, query results are set in the results
field of the response payload, while pagination metadata is set in the pagination
field.
As for the possibility to query based on current search result, you would have to expand a little, because your question is a bit unclear.
var express = require('express');
var mysql = require('mysql');
var Promise = require('bluebird');
var bodyParser = require('body-parser');
var app = express();
var connection = mysql.createConnection({
host : 'localhost',
user : 'myuser',
password : 'mypassword',
database : 'wordpress_test'
});
var queryAsync = Promise.promisify(connection.query.bind(connection));
connection.connect();
// do something when app is closing
// see http://stackoverflow.com/questions/14031763/doing-a-cleanup-action-just-before-node-js-exits
process.stdin.resume()
process.on('exit', exitHandler.bind(null, { shutdownDb: true } ));
app.use(bodyParser.urlencoded({ extended: true }));
app.get('/', function (req, res) {
var numRows;
var queryPagination;
var numPerPage = parseInt(req.query.npp, 10) || 1;
var page = parseInt(req.query.page, 10) || 0;
var numPages;
var skip = page * numPerPage;
// Here we compute the LIMIT parameter for MySQL query
var limit = skip + ',' + numPerPage;
queryAsync('SELECT count(*) as numRows FROM wp_posts')
.then(function(results) {
numRows = results[0].numRows;
numPages = Math.ceil(numRows / numPerPage);
console.log('number of pages:', numPages);
})
.then(() => queryAsync('SELECT * FROM wp_posts ORDER BY ID DESC LIMIT ' + limit))
.then(function(results) {
var responsePayload = {
results: results
};
if (page < numPages) {
responsePayload.pagination = {
current: page,
perPage: numPerPage,
previous: page > 0 ? page - 1 : undefined,
next: page < numPages - 1 ? page + 1 : undefined
}
}
else responsePayload.pagination = {
err: 'queried page ' + page + ' is >= to maximum page number ' + numPages
}
res.json(responsePayload);
})
.catch(function(err) {
console.error(err);
res.json({ err: err });
});
});
app.listen(3000, function () {
console.log('Example app listening on port 3000!');
});
function exitHandler(options, err) {
if (options.shutdownDb) {
console.log('shutdown mysql connection');
connection.end();
}
if (err) console.log(err.stack);
if (options.exit) process.exit();
}
Here is the package.json
file for this example:
{
"name": "stackoverflow-pagination",
"dependencies": {
"bluebird": "^3.3.3",
"body-parser": "^1.15.0",
"express": "^4.13.4",
"mysql": "^2.10.2"
}
}
I taked the solution of @Benito and I tried to make it more clear
var numPerPage = 20;
var skip = (page-1) * numPerPage;
var limit = skip + ',' + numPerPage; // Here we compute the LIMIT parameter for MySQL query
sql.query('SELECT count(*) as numRows FROM users',function (err, rows, fields) {
if(err) {
console.log("error: ", err);
result(err, null);
}else{
var numRows = rows[0].numRows;
var numPages = Math.ceil(numRows / numPerPage);
sql.query('SELECT * FROM users LIMIT ' + limit,function (err, rows, fields) {
if(err) {
console.log("error: ", err);
result(err, null);
}else{
console.log(rows)
result(null, rows,numPages);
}
});
}
});