Set global variable from within a Class

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  • Bruce
    #1

    Set global variable from within a Class

    From within a class instantiation, I'm trying to set the value of a
    global variable. Let's call that variable "x". I know I can do this

    window.x = 5;

    and it will work but I really need to do this:

    x = 5;

    The above works in Firefox 2 but not in IE6. Actually, I'm trying to
    do this

    eval("x = 5");

    For reasons that are too long to explain, I can't do this

    eval("window.x = 5");

    (which I realize would also work) because I can't alter the variable
    name. It has to be "x"

    Any thoughts on how I can do this within the scope of a Class? I know
    this is non standard and might seem odd or inadvisable but it's a long
    story that will be solved if someone can help with my problem.

    Tags: None
    • Bruce
      #2
      Re: Set global variable from within a Class

      Never mind. The cause of my problem is something completely different.
      See the thread "id names are global variables?"

        Comment

        • Jeremy J Starcher
          #3
          Re: Set global variable from within a Class

          On Thu, 02 Oct 2008 11:19:26 -0700, Bruce wrote:

          Are you *sure* this is a good idea?
          eval("x = 5");
          Eval is very seldom the correct tool to use.
          >
          For reasons that are too long to explain, I can't do this
          >
          eval("window.x = 5");
          If you *must* use eval, why can you not:
          { eval("x = 5"); window.x = x; }
          Any thoughts on how I can do this within the scope of a Class? I know
          this is non standard and might seem odd or inadvisable but it's a long
          story that will be solved if someone can help with my problem.

          Tested in Fx 3.0.2, IE6 and Opera (something)

          <html>
          <head>
          <title>Test</title>
          </head>
          <body>

          <script type="text/javascript">

          function w(s)
          {
          document.write( s + "<br>");
          }

          var _global = (function() {return this})();
          var x = 10;

          (function() {
          var x = 5;
          w("Anon function start");
          w("Inner: x= " + x);
          w("_global.x= " + _global.x);

          w("Showing we don't get a primitive reference");
          x = _global.x; // This makes a COPY of _global.x
          x = 8; // And this line doesn't affect global x at all
          w("Inner: x= " + x);
          w("_global.x= " + _global.x);


          w("Anon function inside an anon function finds the 'closest' x");
          (function() { // Even in a new scope, it will find "inner_x" first.
          x = 18;
          })();
          w("Inner: x= " + x);
          w("_global.x= " + _global.x);


          w("As does eval");
          eval("x = 22");
          w("Inner: x= " + x);
          w("_global.x= " + _global.x);


          // Note: I CANNOT actually recommend that someone USE this method.
          // The use of "with" is considered evil by many for very good reason.
          // If this is the "solution" to a problem, I'm willing to wager you
          have
          // have far bigger problems.
          //
          // "with" is considered bad form by many. Don't do it.
          w("But the WITH statement is ... magic");
          with(_global) {
          x = 15;
          }
          w("Inner: x= " + x);
          w("_global.x= " + _global.x);


          w("But the WITH statement is ... magic -- with eval");
          with(_global) {
          eval("x = 25");
          }
          w("Inner: x= " + x);
          w("_global.x= " + _global.x);

          })();


          w("And the end, we have: global x= " + x);

          </script>

          </body>
          </html>

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