Can't check for undefined locals

[samholmes]

I can't do typeof someUndefinedLocal == 'undefined' because that will give me an error output saying, "someUndefinedLocal is undefined". Normally, I would be able to do this in JS just fine. If EJS is truely "Embedded JavaScript" then it should at least act like it. For now I have to use typeof this.someUndefinedLocal == 'undefined', but I really wish didn't.

[samholmes]

Actually, I'm not even sure if this.someUndefinedLocal references the local someUndefinedLocal in ejs. x__x

[samholmes]

typeof someUndefinedLocal... works only only if not buffered.

this.someUndefinedLocal does not reference the local.

In conclusion, this issue is about bringing support for undefined locals in buffered outputs <%- %> and <%= %>.

[RandomEtc]

Have you tried hasOwnProperty('someUndefinedLocal') to check for the existence of a parameter? It's not pretty but it might be nicer than checking for undefined.

[ForbesLindesay]

I think you're probably misunderstanding this. EJS literally takes your javascript and puts it in a function then executes it.

Both of these work fine:

<%= typeof foo === "undefined"?'foo is undefined':foo %>
<%- typeof foo === "undefined"?'foo is undefined':foo %>

This won't work, not because of a bug in EJS, but because they don't make sense as javascript.

<%= if(true){"Truth"}else{"False"} %>

Buffered EJS can only accept things that would work as an argument to a function (specifically Array.push). Consider the following invalid JavaScript

function doSomething(arg){
    console.log(arg);
}

doSomething(if(false){"Truth"}else{"False"});

It's the same reason you can't use while, for etc. inside a buffered block (unless you also wrap it in a self-calling function.

If that's not what's causing your problem, then I apologise. Perhaps you could post the full contents of the buffered block that causes the failure.

P.S. I didn't have a variable called foo defined inside my view when running these tests.

[web-bert]

Have you considered implementing a 'safe navigation operator', similar to Grails, which uses a question mark? I found it quite useful.

My use case is a bit different, in that I have an object for the values of a form (because the names conflict with some locals), so for each value attribute on the form elements, I want to pre fill the value; it would be nice to use a compact syntax for that:

<input type="text" value="<%= form?.title %>">
< textarea><%= form?.message %>

Currently I am creating a form object and all its properties to keep the view logic simple, as I don't want to have this in each value:

<%= typeof form === 'undefined' || typeof form.title === 'undefined' ? '' : form.title %>

I know it is deviating slightly from standard JS, but in the context of views I think it is acceptable? It also might make it easier to basically replace the ? with a typeof, so maybe the syntax should be:

<input type="text" value="<%= form?.title? %>">
< textarea><%= form?.message? %>

So it will keep the implementation logic simple?

[ForbesLindesay]

I think that is probably too much bloat to put in ejs itself (it's a fairly complex operation requiring AST manipulation. If it should exit, it should be a language level feature of JavaScript, not a feature specific to Embedded JavaScript.