if statements with underscore.js

Question

[Note: This question is very similar, but not quite the same.]

I'm trying to do if statements with underscore templates. I have tried:

<% if (_id) { %><%=_id %><% } %>

and

<% if (_id) { _id } %>

and

<% if (_id) { <%= _id %> } %>

and a bunch of other combinations, but I always get the error

ReferenceError: _id is not defined

Any suggestions?

Michael Krelin - hacker · Accepted Answer · 2011-12-23 23:29:50Z

6

I have no idea what is your code, but _id is obviously an identifier. The problem, though, that you do not have _id defined.

As for suggestion, I'd probably suggest that you define it or use the one that is defined. It's hard to give you a better suggestion with zero context.

EDIT: you probably want if(typeof _id != 'undefined') instead.

edited Dec 23, 2011 at 23:29

answered Dec 23, 2011 at 23:01

Michael Krelin - hacker

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5 Comments

Randomblue Over a year ago

Here is the context. I render the template by passing an object wit properties. It turns out that sometimes _id is not one of the properties of that object. In that case, I just want to show nothing, but not error out.

Michael Krelin - hacker Over a year ago

Because if you reference undefined variable you get the not defined error with some javascript engines.

Randomblue Over a year ago

Aha. Could you link to further information regarding this. Because I constantly use the pattern if(variable) { ... } where variable could be undefined?

Michael Krelin - hacker Over a year ago

Here? stackoverflow.com/questions/138669/… ? :)

Michael Krelin - hacker Over a year ago

You probably refer to object properties (if(a.b)) or function parameters. I think it works better in these cases.

David Fregoli · Accepted Answer · 2013-06-12 12:30:11Z

0

A bit old, but this is how I solved a similar problem:

inside your model:

var Model = Backbone.Model.extend({

    defaults: {
        field1: null
    }

});

then in your template you can do:

<% if (field1) { %>
    ...
<% } else { %>
    ...
<% } %>

edited Jun 12, 2013 at 12:30

answered Jun 12, 2013 at 10:13

David Fregoli

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