Thanks for the suggestion!.... but... I missing some part of your answer.
I guess I understand the difference btw global, this.property, and var
local. And then, I understand why it not works. What I don't understand is
how to circumvent/solve the problem. I don't know if your answer is:
a- " you'll get the answers :) " and then, you will know that it's
impossible to solve, or too weird
b- you'll get the answers :) " and it's possible in this (simple)
way.....etc...
AFAIK, it's "a". Am I right?
My problem is:
- module1 requires module2
- I want to use the exposed functions of module2 as they were defined in
module1, using dynamic names. That is, it's not a solution
var module2 = require('module2');
var Function2 = module2.Function2;
Usually, I did a bit of experiment at REPL. I found that this works:
var name = 'Function2';
this[name] = ...
var obj = new Function2(); // without using this
BUT it's only works at REPL. So, encouraged by this discovery (I expected
it will not work), I hoped to make it works in other context.
Now, I understand why it is work in REPL. Notably, in REPL
this == global
so it's possible to emulate
var foo = ...
with something like (pseudocode)
name = 'foo'
var [name] = .....
writing
name = 'foo';
this[name] = ...
and then foo is available "as if it is" a local var.
But inside a running .js, this is not equal to global. I was tricked by
REPL ;-)
So, the better solution I found so far is to put something like this in
module1:
//
http://stackoverflow.com/questions/5625569/include-external-js-file-in-node-js-app
var fs = require('fs');
var vm = require('vm');
var includeInThisContext = function(path) {
var code = fs.readFileSync(path);
vm.runInThisContext(code, path);
}.bind(this);
includeInThisContext(__dirname + '/module2.js');
console.log(foo); // it's defined
where module2 define foo:
foo = {};
BUT IN MY CASE, module2 doesn't define the functions at its own context:
https://github.com/ajlopez/SimpleTags/blob/master/lib/simpletags.js
it uses an array to dynamically define and export functions. I never have
function h1() {
}
function h2() {
}
defined at module2 context. And I don't want this. My DSL defines a
function for each HTML tag.
Now, I want to have these dynamically defined functions from
module2 accessible in outer module1, as they were local to it.
I could write inside my module,
var h1 = makeTag('h1');
var h2 = makeTag('h2");
...
....
for dozens of tags, and then use something like includeInThisContext....
but I feel it's too weird.
Apparently, my problem is: I didn't find a way to define a local var with a
dynamic name.
The original DSL in Ruby:
https://github.com/dlitvakb/deklarativna/blob/master/test/test_deklarativna.rb
use "include dslmodule". And inside the dsl module, it defines dynamically
named functions at module top level. So the functions are automatically
available to the module that makes the includes.
That is the "trick" I didn't found how to emulate in
Node.js/require/CommonJS world.
Some links in my research:
http://stackoverflow.com/questions/5833978/javascript-how-to-use-dynamic-local-variables
http://stackoverflow.com/questions/5094862/how-do-i-access-a-local-variable-dynamically-via-a-string-form-of-its-name-fro
http://stackoverflow.com/questions/598878/how-can-i-access-local-scope-dynamically-in-javascript
http://stackoverflow.com/questions/2336508/javascript-get-access-to-local-variable-or-variable-in-closure-by-its-name
http://stackoverflow.com/questions/1119335/javascript-local-variable-declare
The better approach I found in these links is to use eval (!!??):
eval("var "+name+ " = ....");
Am I right? the only ways are the above ones? Or is another way?
Any suggestions?
Angel "Java" Lopez
On Sat, Jul 7, 2012 at 9:27 AM, Mariusz Nowak <[email protected]> wrote:
> @ajlopez get to know how variable scoping in JavaScript works (what is
> global, how this and how local variable works), and you'll get the answers
> :)
>
>
> On Saturday, July 7, 2012 2:11:56 PM UTC+2, ajlopez wrote:
>>
>> Hi people!
>>
>> A very simple question. When I write in the Node repl:
>>
>> this.foo = 'bar';
>> console.log(foo);
>>
>> it's ok, foo is defined. But writing that code in file.js and running
>>
>> node file.js
>>
>> then foo is not defined.
>>
>> Or require('file.js'), then foo is not defined.
>>
>> Any way to define a variable in the "current context"? Apparently, "this"
>> properties and "current context" top variables are the same in REPL, but
>> they are not the same in .js, or inside a required module.
>>
>> I want to do this in a dynamic way:
>>
>> name = 'foo';
>> // ...
>> this[name] = 'bar';
>>
>> so
>>
>> foo = 'bar';
>>
>> is not a solution in my context.
>>
>> I could use:
>>
>> global[name] = 'bar';
>>
>> but I want to expose the new "current context" top variables only in my
>> "current context" without pollute the global environment.
>>
>> I encountered this problem when coding a simple HTML DSL:
>> https://github.com/ajlopez/**SimpleTags/blob/master/test/**exportsTo.js<https://github.com/ajlopez/SimpleTags/blob/master/test/exportsTo.js>
>> I want the DSL functions to be accesible as:
>>
>> require('simpletags').**exportsTo(????); // ???? == global? this? Now, I
>> should use global to make it works in any situation
>>
>> then, use the exported function as functions in current context:
>>
>> html(body(h1("TheNextBigThing"**)));
>>
>> instead
>>
>> var st = require("simpletags");
>>
>> st.html(st.body(st.h1("**TheNextBigThing")));
>>
>> Any other way?
>>
>> TIA
>>
>> Angel "Java" Lopez
>> http://ajlopez.wordpress.com
>> @ajlopez
>> gh:ajlopez
>>
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