Can routes in Express be declared with a loop?

Question

When I try to declare the below, the index page works, but the other pages all 404. I know it's not a problem with my links.js file, since when I hard code the output of the for loop, the links all work. I console.logged the router object and it shows the info in the stack. But when I try to open any of the links, they 404, and nothing is logged to the console.

Is it not possible to declare routes using a for loop? Code is copied below.

var express = require('express');
var router = express.Router();
var config = require('../models/config.js');
var links = require('../models/links.js');

// homepage
router.get('/', function(req, res, next) {
  res.render('index', { title: config.title });
});

for (var i = 0; i < links.length; i++) {
    router.get(links[i].regex, function(req, res, next) {
        console.log("trying to open " + links[i].url);
        res.render(links[i].url, { title: links[i].title, link: links[i] });
    });
}

module.exports = router;

Answer 1

The problem is that you don't have a proper closure around the current value of links[i]. By the time your routes get called, i === links.length, so links[i] points to something other than what you expect.

The easiest way around this is to simply use links.forEach() instead, which creates/uses a closure:

links.forEach(function(link) {
  router.get(link.regex, function(req, res, next) {
    console.log("trying to open " + link.url);
    res.render(link.url, { title: link.title, link: link });
  });
});