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Re: eval - how to

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Cezary Tomczyk wrote:

> According to "Better not use eval() because ... ":
> 
> How to use eval in a correct way?
> 
> For example when I'll get the JavaScript (or any other EcmaScript
> implementation) code through XMLHttpRequest then how to safely eval the
> code?

(It's _ECMAScript_, published by _Ecma_ International, for historical 
reasons.)

The only way to safely use eval() is a) not to use it or b) to be sure that 
you are using a conforming implementation of ECMAScript Ed. 5 or later 
(where the scope chain of eval code is empty; which you really cannot be 
sure about in a browser). 

But if you really must use eval(), and want to/need to parse JSON(-like 
data) with it (instead of with JSON.parse()), be sure that the literal is 
evaluated in an expression context:

   var obj = eval("(" + JSON_object_string + ")");

The `(' and `)' would be necessary because the `{' and `}' of an object 
literal also delimit a Block statement, whose production takes precedence in 
a statement context.


PointedEars
-- 
Danny Goodman's books are out of date and teach practices that are
positively harmful for cross-browser scripting.
  -- Richard Cornford, cljs, <cife6q$253$1$8300dec7@news.demon.co.uk> (2004)

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eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-09 12:47 +0100
  Re: eval - how to Asen Bozhilov <asen.bozhilov@gmail.com> - 2012-11-09 05:53 -0800
    Re: eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-09 22:28 +0100
      Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-10 10:23 +0100
      Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-10 11:15 +0100
        Re: eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-11 00:35 +0100
          Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-11 20:34 +0100
    Re: eval - how to Dr J R Stockton <reply1245@merlyn.demon.co.uk.invalid> - 2012-11-10 22:42 +0000
  Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-09 17:46 +0100
    Re: eval - how to Tim Streater <timstreater@greenbee.net> - 2012-11-09 17:00 +0000
      Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-09 18:19 +0100
    Re: eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-09 22:49 +0100
      Re: eval - how to Asen Bozhilov <asen.bozhilov@gmail.com> - 2012-11-09 16:40 -0800
        Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-10 11:36 +0100
          Re: eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-10 13:29 +0100
            Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-10 13:55 +0100
              Re: eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-10 14:17 +0100
                Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-10 20:50 +0100
                Re: eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-10 22:54 +0100
                Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-11 15:22 +0100
                Re: eval - how to Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2012-11-11 16:24 +0100
                Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-11 19:23 +0100
          Re: eval - how to Asen Bozhilov <asen.bozhilov@gmail.com> - 2012-11-11 10:40 -0800
            Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-11 20:41 +0100
              Re: eval - how to Asen Bozhilov <asen.bozhilov@gmail.com> - 2012-11-11 13:34 -0800
                Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-11 23:03 +0100
      Re: eval - how to Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-10 10:21 +0100
  Re: eval - how to SAM <stephanemoriaux.NoAdmin@wanadoo.fr.invalid> - 2012-11-10 04:16 +0100

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