I'm currently developing a basic local image server that supplies images to a web application along with some JSON data. The web app includes pagination functionality which triggers a get request "/images?page=X&limit=200" to an express.js server, receiving back the JSON files in one array. I aim to utilize the browser's internal caching mechanism so that when a user navigates to a previous page, the express.js server returns an ETAG. Could someone advise me on how to achieve this using express.js? Specifically, for this project, I only need the calculation of the ETAG to involve three parameters: the page, directory, and limit (ignoring the entire JSON body). Since this setup is meant for local use, I prefer the server to handle the heavy lifting as it should be quicker than relying solely on the browser. I came across https://www.npmjs.com/package/etag which looks promising, but I'm unsure about integrating it with express.js.
Below is a snippet of the express.js code I have at the moment:
var express = require('express');
var app = express();
var fs = require('fs');
app.get('/', async (req, res) =>{
let files = [];
let directory = fs.readdirSync("mypath");
let page = parseInt(req.query.page);
let limit = parseInt(req.query.limit);
for (let i = 0; i < limit; ++i) {
files.push(new Promise((resolve) => {
fs.readFile(files[i + page * limit].name, (err, data) => {
// format the data for UI convenience
resolve(JSON.parse(data));
});
});
}
let results = await Promise.all(files);
// calculate an etag here and append it to the results.
res.send(results);
});
app.listen(3000);