I recently watched a JavaScript video tutorial containing code similar to this one:
(function (){
var b = 10,
c = 20,
d = 50;
var e = function(){
return b + c + d;
};
return e();
}());
This is a common JS coding pattern. The author said that this is an example of a procedural approach in Javascript code. I don't understand that, can you please explain.
Let's start by saying the above is a self-invoking anonymous function:
A self-invoking anonymous function runs automatically/immediately when you create it and has no name, hence called anonymous.
The above is a fairly poor example in my opinion, but consider the following change:
var f = (function (){
var b = 10,
c = 20,
d = 50;
var e = function(){
return b + c + d;
};
return e();
}());
console.log(f);
We've taken the above code and added a var f = in front of the function. This returns the value of e() from the inner function to f and now you have a value f to be used elsewhere. Since the variables b, c, d, e are declared within the function scope of the anonymous function, we can ensure that they will not be tampered with. This is a way to do private variables in JavaScript. Now say you had 10 + 20 + 50 may places within your code. You could run this anonymous function at the beginning and substitute those occurrences with f. This idea of abstracting out code into various procedures is why it's referred to as Procedural Programming.
Procedural programming uses a structured approach to coding the program where the functionality of the program is broken down into a number of functions or subroutines to make it easier to follow and reduce the need to repeat code.
This is mainly used to make code easier to read, easier to follow/debug and lets you abstract commonly used chunks of code into well written snippets of code.
Purpose of Self-Invoking Functions
and this moves you into Closures
