|| operator not working as expected in EJS

Question

I have this EJS code:

<link rel="stylesheet" type="text/css" href="/public/stylesheets/<%= css || 'default' %>.css" />

I thought that, when css was undefined , this would evaluate to "/public/stylesheets/default.css" , but instead it throws the error

css is not defined

Why? Is this a quirk of EJS, or am I misunderstanding something?

Answer 1

As VLAZ says:

It says that css is not defined rather than undefined . Two different concepts. If it's not defined, it's never declared and/or cannot be reached from the current and enclosing scopes. undefined means it's declared but no value is assigned to it.

I was able to solve my problem using customcommander 's solution:

Rather than

css || 'default'

which throws an error, use

typeof css === 'undefined' ? 'default' : css