Subj : How to use scripts to create persistent objects?
To   : netscape.public.mozilla.jseng
From : wayne
Date : Mon Sep 13 2004 08:41 am

According to the JavaScript C Engine Embedder's Guide:

"NOTE: You can also use scripts to create persistent objects, too."

However, I am unable to figure out how to accomplish this (and was
unable to find previous newsgroup postings explaining this process
after doing a *very* extensive search).

JS_EvaluateScript() on the following JS:

var m = new MyObject( 5 );

function MyObject( num )
{
  this.num = num;
}

alert( 'm.num = ' + m.num );

document.write( '<div id="m1"></div>' );
var o = document.all[ "m1" ];
o.m = m;
alert( 'o.m.num = ' + o.m.num );
var p = document.all[ "m1" ];
alert( 'p.m.num = ' + p.m.num );

Each alert( X.m.num ) prints "5" as expected. Then, we immediately do
another JS_EvaluateScript() (same JSContext & Runtime) on the
following JS:

var q = document.all[ "m1" ];
alert( 'q.m.num = ' + q.m.num );

but instead of printing "5", we get "TypeError: q.m has no properties
line 0".

It may not be possible to answer without knowing all the C code behind
this, but why does the technique of setting a property in the object
held in the document.all array at "m1" appear to work within one
script execution, but not subsequent script executions using
essentially the same code? (By the way, replacing the second JS code
segment with "alert( 'm.num = ' + m.num );" does output "5".)

Any help and guidance would be most appreciated.

Thank you,

Wayne

.