Encountered some code that's using IIFEs in an expression rather than just a normal function.
var custom_type = (function() {
return $('#myDiv').attr('custom_type');
})();
Normally I would write this as something like:
var custom_type = function() {
return $('#myDiv').attr('custom_type');
};
What's the reason for the IIFE? The only thing I can think of is that the IIFE might assign the custom_type variable only once at the beginning whereas the second might continue to check for the updated type every time the variable is referenced.
In this example, you can dispense with the function altogether and just do:
var custom_type = $('#myDiv').attr('custom_type');
However in general you can use an IIFE for more complex "just-in-time" computation of variable assignments - I like to use them if I need to iterate over something, so I can have i without polluting the current scope.
In your second example, though, the result is completely different - you will need to call the function custom_type() to get the current value, whereas the first piece of code will get its value once, and the variable will hold that value.