In the Google tutorial for implementing Google+ sign-in in Flask application, I discovered that the developer often uses an awkward way of executing JavaScript code:
Instead of doing
var a = foo(bar);
I see this:
var a = (function() {
return foo(bar);
})();
What is the reason to do it the weird way?
This is a poor example. Consider the following:
var a = (function(){
var ret = {};
ret.test = "123";
function imPrivate() { /* ... */ }
ret.public = function() { imPrivate(); }
return ret;
})();
a will contain the varible test and the function public, however you can not access imPrivate. This is the common way to handle public vs private variables;
See Why is this function wrapped in parentheses, followed by parentheses? for more info.
###
var a = (function() {
return foo(bar);
})();
In this case this is really unnecessary, but this is not wrong and it will not throw an error.
But IIF some times uses like module pattern:
var a = (function() {
/* some other code in own scope */
return foo(bar);
})();
In this case IIF is just a module which exports something outside.
###
The closure function is used to encapsulate some of the attributes / methods in the function. Much like the private / public principle from other languages.
You can find more on this topic here under Module Pattern