Mustache - How to detect array is not empty?

Question

I want to implement the following logic with Mustache:

{{#if users.length > 0}}
    <ul>
        {{#users}}
            <li>{{.}}</li>
        {{/users}}
    </ul>
{{/if}}

// eg. data = { users: ['Tom', 'Jerry'] }

Should I modify the users structure to meet the need? For example:

{{#hasUsers}}
    <ul>
        {{#users}}
            <li>{{.}}</li>
        {{/users}}
    </ul>
{{/hasUsers}}

// eg. data = { hasUsers: true, users: ['Tom', 'Jerry'] }

Yes, I believe you are going to have to modify the data like you've done with `hasUsers`. Another option is using the more robust [Handlebars](http://handlebarsjs.com/) which handles this exact case on their homepage. — maxbeatty, Jul 25 '12 at 18:26

score 88 · Accepted Answer · edited Jan 13 '15 at 13:39

88

Sorry, this may be too late. But I had similar requirement and found a better way to do this:

{{#users.length}}
    <ul>
        {{#users}}
            <li>{{.}}</li>
        {{/users}}
    </ul>
{{/users.length}}
{{^users.length}}
    <p>No Users</p>
{{/users.length}}

Working sample here: http://jsfiddle.net/eSvdb/

edited Jan 13 '15 at 13:39

Kara Brightwell

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answered Jul 27 '13 at 11:14

Ambarish Chaudhari

896
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10

Please note though, this is not a standard mustache function. It varies depending on Mustache implementation. – corgrath Mar 04 '16 at 09:06
7

Never too late on SO :) – jClark Nov 30 '17 at 16:31
I can confirm, as @corgrath said, that this is implementation-dependant: it isn't working with samskivert's Java Mustache library. – penguin86 Jan 11 '18 at 16:51
#users.length - check if array is/or not null – Avtandil Kavrelishvili Sep 29 '20 at 21:13
3

Try `{{#users.size}}` with the Java implementation. – Tim Hennekey Apr 13 '22 at 16:09
`{{#users.size}}` works also for C# (length doesn't) – Maxim Zabolotskikh Oct 04 '22 at 09:29

score 44 · Answer 2 · edited Oct 17 '17 at 15:29

44

Using {{#users.length}} works great if you want the inner statement to repeat for every element of the array, but if you only want a statement to only run once, you can use:

{{#users.0}}
...
{{/users.0}}
{{^users.0}}
...
{{/users.0}}

edited Oct 17 '17 at 15:29

Adriano

19,463
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answered Apr 02 '15 at 17:04

dessalines

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7

this way also works well with php since arrays doesn't have length property. – JacopKane Apr 02 '15 at 22:29
Will fail if `users` is an array of arrays, though. – Tgr Sep 09 '17 at 11:30
1

it works! but it's not documented in the official mustache doc. – Roman T Jun 14 '18 at 13:58
Great idea I was having just this problem! :) – Phate Apr 16 '20 at 20:45

score 1 · Answer 3 · answered Dec 25 '21 at 08:29

I'm using chevron for Python. Since {{#users.length}} is implementation-dependent as described in previous answers, and doesn't work for me in Chevron, I return an object in my code which only contains the list if the list is non-empty. Presumably this technique would work for other languages too.

users = ["user1", "user2", "userN"]
user_obj = {"user_list": users} if len(users) > 0 else {}
template = """
{{#users}}
<ul>
    {{#user_list}}
    <li>{{.}}</li>
    {{/user_list}}
</ul>
{{/users}}
"""

chevron.render(template, {"users": user_obj})

Mustache - How to detect array is not empty?

3 Answers3

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