69 lines
1.9 KiB
JavaScript
69 lines
1.9 KiB
JavaScript
/** This module defines a express.Router() instance
|
|
* - supporting offset=<number> and limit=<number>*
|
|
* - calls next with error if a impossible offset and/or limit value is given
|
|
*
|
|
* Note: it expects to be called BEFORE any data fetched from DB
|
|
* Note: it sets an object { limit: 0, skip: 0 } with the proper number values in req.locals.limitskip
|
|
* Note: it sets an Error-Object to next with error.status set to HTTP status code 400
|
|
*
|
|
* @author Johannes Konert
|
|
* @licence CC BY-SA 4.0
|
|
*
|
|
* @module restapi/limitoffset-middleware-mongo
|
|
* @type {Router}
|
|
*/
|
|
|
|
// remember: in modules you have 3 variables given by CommonJS
|
|
// 1.) require() function
|
|
// 2.) module.exports
|
|
// 3.) exports (which is module.exports)
|
|
'use strict';
|
|
|
|
const express = require('express');
|
|
const router = new express.Router();
|
|
const logger = require('debug')('middleware:offsetlimit');
|
|
|
|
|
|
// the exported router with handler
|
|
router.use((req, res, next) => {
|
|
let offset = undefined;
|
|
let limit = undefined;
|
|
const offsetString = req.query.offset;
|
|
const limitString = req.query.limit;
|
|
let err = null;
|
|
|
|
|
|
if (offsetString) {
|
|
if (!isNaN(offsetString)) {
|
|
offset = parseInt(offsetString);
|
|
if (offset < 0) {
|
|
err = new Error('offset is negative');
|
|
}
|
|
} else {
|
|
err = new Error('given offset is not a valid number ' + offsetString);
|
|
}
|
|
}
|
|
if (limitString) {
|
|
if (!isNaN(limitString)) {
|
|
limit = parseInt(limitString);
|
|
if (limit < 1) {
|
|
err = new Error('limit is zero or negative');
|
|
}
|
|
} else {
|
|
err = new Error('given limit is not a valid number ' + limitString);
|
|
}
|
|
}
|
|
if (err) {
|
|
logger('problem occurred with limit/offset values');
|
|
err.status = 400;
|
|
next(err);
|
|
} else {
|
|
res.locals.limitskip = {}; // mongoDB uses parameter object for skip/limit
|
|
if (limit) res.locals.limitskip.limit = limit;
|
|
if (offset) res.locals.limitskip.skip = offset;
|
|
next();
|
|
}
|
|
});
|
|
|
|
module.exports = router;
|