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Now let's stick to functions for the moment

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because there's one other thing you should be aware of

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when we talk about functions

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and that's stat behind the scenes,

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internally, functions are in the end, just objects.

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And that can be confusing because we did learn

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that objects are these things with those curly braces,

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which you create like this.

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And then you could add a name which has max and the age,

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which is 32 and do something like that.

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That's an object.

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That's what we learned before.

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And objects have these key value pairs,

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which are called properties,

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which you can access with the dot notation

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to set a new value or to read the value.

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And you can also add methods to objects,

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but functions are also objects.

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And for that let's console log sumUp without parentheses.

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So just the name of the function here.

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With that, we are not executing the function,

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but instead we are just getting a reference

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to that function.

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We're just pointing at that function and we are therefore

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logging the function itself.

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Instead of the result of calling the function.

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That's what we do here instead, here in this line,

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we output the result of calling that function because

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we do have those parentheses here.

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On the other hand in this line,

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we are just outputting the function itself.

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And if we do that and I save everything here,

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if we execute this file,

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what we see is this strange syntax here, function sumUp.

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Now that's not telling us too much.

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It tells us that we have some function here,

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which is called sumUp,

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but that's actually just how NodeJS outputs

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this function object.

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If we do the same thing in the browser,

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simply because there we get a, a nicer, more useful output,

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then we'll see something different.

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And for that, I opened a brand new tab

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and then the console here in the dev tools,

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because in here, we can actually also write

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some JavaScript code that will be evaluated.

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And therefore here I'll just add a function called add,

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which accepts two numbers, let's say,

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and which then just returns.

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Num one plus num two,

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and we're writing it all in one line here.

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And it's a very simple function because here,

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I don't want to talk about this function too much,

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but instead about that object, which every function is.

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So for that, I'm writing a function here.

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If I console log at here in the browser dev tools

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in this console, which you can also use

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to play around with some dummy code,

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as you see here, and I hit enter here,

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then we already get a slightly different output.

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And if we now replace console log with console dir,

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which is more useful when outputting objects,

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then you also get a little arrow here, which you can click.

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And if you click it, you'll see a couple of properties.

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These are key value pairs, and these are key value pairs,

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of an object, of the function object that every function is.

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Now, these are not properties, which you added manually.

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We haven't added any properties at all to this function.

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Instead, these are properties which are

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inferred automatically.

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For example,

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the name of the function is stored in a separate property

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or the number of arguments.

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The number of parameters this function takes

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is stored in a length property.

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Now, why do you need to know that, if you don't set

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those properties on your own?

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Well, not because we will start setting properties

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on our functions, but because this is something

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we encountered before already,

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when we used express this express package,

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then we did require it in our NodeJS code.

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And we executed it like a function to create

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this app object here.

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That's what we did before.

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Now in other places of the code.

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We however, used that same express function,

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which it seems to be, to then all of a sudden access

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properties on that function.

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And we were able to do that because the team that developed

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the express package added some custom properties

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to this express function, to add more functionality

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to that express thing that you can use in your code,

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you could do something similar in your own code

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with your own functions as well.

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You can use the sumUp function and use the dot notation

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to add some property.

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You can do that for all objects that you add new properties

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by simply accessing properties that don't exist yet and

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storing new values in them.

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But of course, typically you don't do that

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because it's not too useful.

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The team that developed the express package did that though.

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And I'm just emphasizing this again here.

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So that it's clear that even though we

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don't typically do that, we can do that.

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We can add properties to functions

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because functions behind the scenes are all just objects,

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special kinds of objects, but still objects.

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And that's why express could both be executed as a function

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and then be used like a object when we access properties.

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And that's just something which I wanted to bring up again

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to make it clear why that code worked the way it did work.