---
title: Curious JavaScript Quirks Found Rewriting 'Hello, World'
author: George Mandis <george@mand.is>
date: 2020-02-10
description: Strange discoveries in the pursuit of ill-advised JavaScript
tags: post, post, programming, javascript, strangem useless
---

I have a silly project on GitHub right now called [101 Hello Worlds](https://github.com/georgemandis/101-hello-worlds). The goal is to come up with 101 unique and convoluted ways to write a function that returns a simple string: *Hello, World*. It's fun, in the spirit of [code golfing](https://codegolf.stackexchange.com/) and requires you to think outside the box.

Over the course of creating and reviewing submissions for the project I've come across a couple curious JavaScript quirks worth sharing:

## Requiring Modules Inside Evals Invoked by Reference

During a recent pairing session with a fellow [Recurse Center](https://www.recurse.com/scout/click?t=151b3c977197fc57d3ab8ce968bce35e) attendee we stumbled across an odd bit of JavaScript behvior: if you try to `eval` a `require` statement it will only work if `eval` is called directly and will fail if it's invoked by reference.

What does that mean in plain English? It's probably easier to show in code.

This should work:

```
eval("require('./module.js')")
```

This should **not** work:

```
const e = eval;
e("require('./module.js')")
```

You will get the error message `require is not defined`, which is probably a first if you were like us.

Why is that? The [description over at Mozilla Developer Network](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval#Description) says evals invoked by reference will work in the "global" scope instead of the "local" scope. I guess that makes `require` unavailable to it in this context, for whatever reason.

Adding to the confusion, when I try these exact same examples from the Node.js REPL **both** approaches work for me.

Obligatory warning: [Never use eval()!](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval#Never_use_eval!).

## Tagged Template Strings

Not to be confused with your run-of-the-mill [template literals](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals), which I use quite often and find very useful.

Did you know you can do this?

```
console.log`wtf`
```

That's not a typo. You're probably used to seeing it formatted more like this:

```
console.log(`wtf`)
```


Wes Bos has a [nice explanation about tagged template strings](https://wesbos.com/tagged-template-literals/) that actually makes sense and even provides a use-case for why you might want them.