Rationale for KM JavaScript-in-browser style: enclose in (function () { ... } )();

[brec]

The first example I used from the late JMichaelTX for a The JavaScript text in front browser condition was in this form:

(function ()( {
    // .... JavaScript code ...
    return theReturnValue
}
)();

as opposed to

// .... JavaScript code ...
theReturnValue

What would be the rationale for the self-executing function () format?

[ComplexPoint]

See the step by step account of the various parts of an IIFE in this post:

Comparing JavaScript for Automation (JXA) and AppleScript

That's right – JavaScript interpreter environments, like Script Editor, and the JavaScript console in browsers, generally have a persistent global name space, containing a whole lot of definitions. It's a crowded space. You can see its contents by running the following one-word JS script in Script Editor: this (You will see a lot of crowded detail appearing in the Script Editor Results panel) If you don't write your code definitions inside a function wrapping, they are just added to this alr…