how to render common variables from app.js to all routes in express

Question

In my Node.js application some variables that render or every route are common.There are around 4-5 variables which render on every route. And I have around 20 routes.

Currently I am doing passing those variables in every route in res.render

Is there a method by which I can pass these common variables in some place '(eg:app.js)` which is being used by every route, so that I can clean up my code a bit.

I use express.js for node and handlebars for template.

EDIT:I think I should explain a bit more

res.render('abc', {
                        commonitem1: 'one',
                        commonitem2: 'two',
                        ...
                   });

-------------------------------------
another route
res.render('xyz', {
                        commonitem1: 'one',
                        commonitem2: 'two',
                        ...
                   });

I want to avoid this repeating in my every routes and want to render it from a common place.

Answer 1

For session or request dependent values you can store those common values in a global variable and then use them directly in res.render. To do that you have following options

• Use app.use to store values :

In your app.js add a middleware which does this for you. Remember to write this middleware before any other routes you define because middleware functions are executed sequentially.

app.use(function(req, res, next){
    res.locals.items = "Value";
    next();
});
//your routes follow
app.use(‘/’, home);

In your routes you can place items directly in res.render like:

res.render('layout', {title: 'My awesome title',view: 'home', item :res.locals.items });

• Use express-session to store values :

If you have express-session installed you can save some data in req.session.item and place them in any route like:

res.render('layout', {title: 'My awesome title',view: 'home', item :req.session.items });