feature request - default filter

[twobit]

trafficstars

Hi, thanks for working on EJS. The following filter has proven useful to me when dealing with possibly undefined keys:

exports.default = function(str, val) {return str || val || '';}

Allows you to use something like this in your template so you don't output 'undefined':

<%=: obj.key | default:'N/A' %> <%=: obj.key | default %>

[rcmachado]

Maybe, when a variable is 'undefined' the view output must be "" (empty string). What do you think?

[AlexNachbaur]

I could see a feature like this being handy. I have a lot of code in my templates for other projects (not based on node.js) that encapsulate the logic to show a default value or placeholder when the parameter doesn't have a value.

[tj]

what is wrong with obj.key || 'foo' ?

[logicplace]

I'd say falsey values is what's wrong with it, but it's not like twobit's filter accounts for that either. Perhaps if it were: exports.default = function(str, val) {return typeof(str)=="undefined"? val : str;} it'd be more useful?

[tj]

yeah typeof is necessary all over ejs/jade stuff. or null == locals[key] ? :

[logicplace]

Oh just realized, too, that || wouldn't be possible in a filter, so although default wouldn't be great on its own it'd be useful with additional filters.

[ebunders]

for this problem it might be better to consider what they call the 'safe navigation operator', in stead of a filter. It works like so:

post?.authors?.[0] where authors is invoked only when post is not null/undefined and [0] is not invoked if authors is not null or undefined. I think this functionality should be part of the <%= => expression.

http://groovy.codehaus.org/Operators#Operators-SafeNavigationOperator%28%3F.%29

[tj]

the foo?.bar? coffeescript thing isn't going to happen, it's really ugly and starts to mess with js expressions which is even worse than the filters right now

[ebunders]

Well, Some things I had to do to do all those undefined checks are pretty messy too:

<div class='fieldgroup'>
    <label for='title'>Title</label>
    <input name='title' <%if(locals.post && post.get('title').value){%> value='<%=post.get('title').value%>' <%}%> />
    <%if(locals.post && post.get('title').errorMsg()){%>
        <div class="error"><%=locals.post && post.get('title').errorMsg()%></div>
    <%}%>
</div>

But then again I can also do some more work in the controller, provinding more convenient model data, so it's not a big deal. I just enjoyed this syntax using groovy, is all.

[tj]

I agree that it's messy, but it's meant to be embedded js, which isn't necessarily ideal for templating but it is what it is

[Vadorequest]

I believe as well this default thing is required in EJS. See: http://stackoverflow.com/questions/29188640/struggle-with-ejs-and-scope-of-not-so-local-variables/29262428

Also, what's <%=:? I've never seen the use of the : before.