Ejs variable persistence? - node.js

Question

I have an express route which filters the month of a blog post and returns the months:
router.get("/months", async (req,res)=>{
try{
let posts = await pool.query(`select * from posts
where MonthName(created_at) = '${req.query.month}'`)
console.log(`select * from posts
where MonthName(created_at) = '${req.query.month}'`)
let tags = await pool.query(`Select tagName from tags`)
filter = req.query.month
res.render("index",{posts,tags,filter})
}
catch(err){
console.log(err)
}
})
It returns the blog posts filter by the month. As you can see I am sending back a filter variable so that in my template I am display the header as in my index.ejs file:
<h2><%= filter %> Blogs</h2>
So that it shows up as April Blogs or whatever filter the user selected
Now the same template is also shated by the default index route:
router.get("/", async (req,res)=>{
try{
let rows = await pool.query(`Select userName as author, posts.* from posts
inner join users on users.id = posts.user_id`)
let tags = await pool.query(`Select tagName from tags`)
res.render("index",{posts:rows,tags:tags})
}
catch(err){
console.log(err)
}
})
By default no filter is applied and a filter variable is not even sent.
Now, the localhost:3000/months/?month=April is perfectly as expected and shows only the blog from April.
But I was expected the localhost:3000 route to throw an error because it is not passing the filter variable but it shows whatever month I selected in the previous route filter.
Only when I terminate the Nodejs server and try to go to the default route do I get:
filter is not defined
But if I go to localhost:3000/months/?month=April and then go back to ``localhost:3000` it loads just fine with month April.
Is it not a good idea to share templates between different routes? How is this possible?

Answer 1

The template is getting cached on first invocation. You might try this answer to disable the view cache in express -
router.disable('view cache');
Another options is listed on the ejs wiki -
router.set('view options', {cache: false});
or you might try disabling in ejs with the additional options parameter -
res.render("index",{posts:rows,tags:tags}, {cache: false})

Answer 2

You need to declare filter and pass a default value, otherwise your renderer will fail.
router.get("/months", async (req,res)=> {
try {
let dbQuery = `select * from posts`;
// handle when req.query.month is not passed.
if (req.query.month) {
dbQuery += ` where MonthName(created_at) = '${req.query.month}'`;
}
const posts = await pool.query(dbQuery);
const dbQuery2 = 'Select tagName from tags';
const tags = await pool.query(dbQuery2);
// declare filter here and assign '' when it's not passed request,
// otherwise your render will fail.
const filter = query.month ? query.month : '';
return res.render("index", {posts, tags, filter});
} catch(err){
// pass error to your main error handler.
return next(err);
}
})
Further i would recommend organising your code better.
// your common shared logic
async function logic({query, params, body}){
const dbQuery = `select * from posts`;
const posts = await pool.query(dbQuery);
return {posts};
}
function handler(req, res, next) {
logic(req)
.then((result) => {
return res.render("index",result);
})
.catch(next);
}
// you can create separate handlers for each requests
// and use the shared logic in handlers.
router.get("/", handler);
router.get("/months", handler);