The simplest template engine for NodeJS

This is the story of how I decided to dump nunjucks and use the best templating engine hack in the world.

…with one line of code.

Background

Node does not seem to have a clear-cut winner when it comes to template engines — for the longest time, I banked on nunjucks but I’ve been wondering if there’s something simpler to take care of templating in small apps. I’m not really bashing nunjucks here, I’m simply wondering if anything else can get the job done without too much fuss.

Mounting the hack

Armed with an express, a couple routes, 2 database queries and more documentation in the README than LoCs, I started writing the following:

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app.get("/my-view", async (req, res) => {
  res.send(render("my-view", {data: await db.getData()}))
})

function render(view, ctx = {}) {
  return fs.readFileSync(`./views/${view}.html`) // WTF do I do with ctx?
}

That’s amazing, I just called a file reader a “template engine”!

Knowing that rendering a file from the filesystem doesn’t cut it (we need to pass and interpret variables etc etc), I then looked to find the most straighforward template engine on the planet and realized lodash has a built-in _.template method:

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var compiled = _.template('hello ${ user }!');
compiled({ 'user': 'tommy' });
// => 'hello tommy!'

Just what I needed — the syntax is not the jinja one but it mirrors template strings, so I can’t complain too much.

Let’s put everything together:

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app.get("/my-view", async (req, res) => {
  res.send(render("my-view", {data: await db.getData()}))
})

function render(view, ctx = {}) {
  return _.template(fs.readFileSync(`./views/${view}.html`))(ctx)
}

Sure, we don’t call res.render, but the difference is very minimal (.render(tpl, ctx) vs .send(render(tpl, ctx))).

Done. No more. That’s it.

Lessons learned

I can be a pretty good liar: I didn’t build a template engine, I simply took advantage of lodash’ own minimalist .template method.

At the same time, though, I love the fact that I’m using a library I anyhow require 99% of the times I’m working in node and I don’t need extra dependencies. It definitely can’t do everything nunjucks does, but, when all you need is rendering a couple templates from your application, this approach works well enough.

And to those who are going to tell me what fs.readFileSync is bad I say: well, it depends.

Do you need to render hundreds of templates per second? Then sure, readFileSync isn’t the most optimized way of doing things. But in a low-traffic, internal app, this just fits the bill.

Adios!