Check if an object is empty in Nunjucks

Question

So I'm using Nunjucks as the templating engine in my Node.js application.

I have an object we'll call var which may or may not be empty.

When it is empty, if I do {{ var | dump }} Nunjucks properly shows that it is an empty object, displaying {}.

The problem is, I can't find any way to check if the object is empty using Nunjuck's {% if condition %} statement. I have tried var.length, var | length, var | first, and just plain var for the condition, but none of them work, they all just evaluate to true (or false), regardless of whether or not var is empty. Does anyone know how to solve this?

EDIT: using {% if var | dump != '{}' %} does work, but seems like a really hacky solution...

EDIT 2: I ended up just creating a custom empty filter for objects which does what I need:

env.addFilter('empty', function(object) {
    return Object.keys(object).length === 0;
});

Faye

Answer 1

Support for accessing an object's length with the length filter was recently added in Nunjucks 2.5.0.

So you can now use:

{% if var|length %}

Advise

God bless you and your family. But can you give some more information on how should I really "understand" that syntax? Because it makes no sense to me :) – Becharm

@Becharm the length filter returns the number of items within an object. If var in this case is an empty object, then it returns a length of 0. This evaluates to false therefore the if condition does not run. On the other hand any positive length would evaluate to true and the condition block would run. – Cavite