On Mar 9, 2010, at 9:18 PM, Aleksandr Rainchik wrote:
Hello!
I've seen some scripts at userscripts.org that start and end in this
way:
// ==UserScript==
// blah..
// blah..
// ==/UserScript==
(function() {
blah...
blah...
})();
Why would someone want to enclose the code with this (function(){...})
(); ?
What does it actually do?
The "anonymous function wrapper" ensures that the script's identifiers
don't collide with identifiers in JavaScript in the page itself. All
of the script's identifiers exist only within the anonymous function,
so they can't "leak out" into the page, or vice versa — the script's
identifiers are all local to the script.
This not only ensures that scripts work, it also addresses serious
security issues with earlier versions of GM. It seems that half of the
history of Greasemonkey is a security story (and one with a happy
ending, as far as I can tell).
If I'm mistaken in how I've explained this, the bright people on this
list will no doubt jump in to correct me.
Dave
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