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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: Reference var in (function(){})()
Date: Tue, 01 Aug 2017 12:40:28 +0200
Organization: PointedEars Software (PES)
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Andrew Poulos wrote:

> There's some code that looks like
> 
> var con = (function() {
>    var opt0 = {},
>        opt1 = {},
>        opt2 = {},
>        opt3 = {},
>        ...

Who is doing such nonsense?
 
>    function x() {
>      //
>    }
> })()
> 
> Within the function x I need to reference each of the (many) "opt"
> objects.

Objects have identity, not name.

> I'd like to reference them in a for loop e.g.
> 
> for (i = 0; i < len; i++) {
>    eval("opt" + i) = ...
> }
> 
> but how can I do it without using eval?

You cannot.  Therefore, use an Array instance –

  var con = (function () {
    var opt = [
      {},
      {},
      {},
      {}
      // , ...
    ];
 
    function x ()
    {
      for (var i = 0, len = opt.length; i < len; ++i)
      {
        // opt[i] = ...
      }
    }

    // x(…)
  })();

– or an Object instance –

  var con = (function () {
    /* “opt” then refers to an object that does not inherit properties */
    var opt = Object.assign(Object.create(null), {
      0: {},
      1: {},
      2: {},
      3: {}
      // , ...
    });
 
    function x ()
    {
      for (var i = 0; i < len; ++i)
      {
        // opt[i] = ...
      }
    }

    // x(…)
  })();

– instead.

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