Is there a difference between the two ways of writing this code?
First Method:
(function(i) {
// Manipulate i here
}(global_variable))
Second Method:
(function() {
// Manipulate global_variable here
}())
What's the reason for passing a global variable to a function if it's already available in that scope?
Providing explicit instructions, this feature allows for the use of a global and creates a convenient alias for quicker typing. Moreover, it enhances performance by eliminating the need to search through all scopes to find the variable in the global scope.
In contrast to regular functions, such as the one shown in your example and not an IIFE, it facilitates testing as it enables easier mocking of the passed-in global.
When it comes to giving variables specific names for different purposes, consider the following examples:
(function(lulu){
//you can use the shorter term "lulu" inside this function
})(LulubellaLekatariLavinaTchaikaEkbatDeSaba)
//A similar approach based on personal preference
(function(){
var lulu = LulubellaLekatariLavinaTchaikaEkbatDeSaba;
//...
})()
Another reason to assign aliases is to encapsulate a value, as shown in this scenario:
(function($){
//$ will maintain the passed-in value even if the global context changes
})(jQuery.noConflict())
This technique allows you to utilize multiple versions of jQuery simultaneously on a single page.
When considering whether or not to make permanent changes to the value of global_variable, it may be wise to opt for the first example in certain situations. For instance, executing this code will only modify the local copy while leaving the global variable unaffected.
global_variable=true; (function(i){ i=false; return i; }(global_variable));
In contrast, the following code directly modifies global_variable:
global_variable=true; (function(){ global_variable=false; }());
It's worth noting that although this variation may appear to alter the global variable, it actually does not due to the creation of a shadow copy when the function is called. This pattern should generally be avoided as it can lead to confusion:
g=true; (function(g){ g=false; return g; }(g));
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