Using EJS with Express

Basic setup

In Express v4, a very basic setup using EJS would look like the following. (This assumes a views directory containing an index.ejs page.

let express = require('express');
let app = express();

app.set('view engine', 'ejs');

app.get('/', (req, res) => {
  res.render('index', {foo: 'FOO'});
});

app.listen(4000, () => console.log('Example app listening on port 4000!'));

There are a number of way to pass specific configuration values to EJS from Express.

View options

This is the most straightforward method, although view options has not been a documented option to use with Express since version 2. Use app.set to set view options:

app.set('view options', {delimiter: '?'});

This method works for all options, even those which cannot be safely passed along with data, like root. It also allows you to set EJS options once, in one place.

Custom render function

This is somewhat less straightforward, but also works well -- completely override the render function:

let ejsOptions = {delimiter: '?'};
app.engine('ejs', (path, data, cb) => {
  ejs.renderFile(path, data, ejsOptions, cb);
});

This method works for all options, even those which cannot be safely passed along with data, like root. It also allows you to set EJS options once, in one place.

App locals

Any properties set on app.locals will get mixed in to the data object passed into a render call for the view engine, and those with names matching known opts properties will be passed to EJS as opts:

app.locals.delimiter = '?'

This does allow you to set your EJS options in one place, but will not work for unsafe options like root.

Passing opts with data

Any properties in the data object for a render call with names matching known opts properties will be passed to EJS as opts:

app.get('/', (req, res) => {
  res.render('index', {foo: 'FOO', delimiter: '?'});
});

This approach means you have to pass EJS options in every single render call, and also does not work with unsafe options like root.