There are several ways that other sites mention to have this working correctly, for example:

For a script to run correctly in eval the way it would run if loaded through an script tag these things have to be set:

Global Object = Activation Object = Variable Object = window

IIRC: This means that if in the eval’d code there’s a variable assignment then it is assigned to the Activation Object. If “this” is used is assigned to the Variable Object. The Global Object that is always “window”.

I haven’t checked this extensively, but different browsers set this objects to different values. Using only window.eval(contents) just forces the Variable Object to be set to window but not the Activation Object that might not be what we expect. Hence the use of “with(window)” is needed to set the Activation Object explicitly and is the only cross-browser solution I have tested personally. When eval’ing, there’s also a different Execution Context than when we include code with an script tag. But that is not possible to change using javascript and might, in some cases, present a problem to eval’d scripts.

There is more information in this site: http://bclary.com/2004/11/07/#a-10

I’m curious what difference it makes to enclose window.eval() in the with statement since you access window.eval explicitly?

Thanks,
-Andrew