Now that we have covered event functions, adding our own custom functions should be pretty easy. Any object, including ones you make during runtime using the curly braces, can have functions attached to them. Not only that, but a variable itself can be a function. You can create functions inside another function and even change what is in an existing function during runtime. Basically, functions are everywhere and they are very flexible. In order to properly make a game, you will need functions. Lots of functions.

So let's create our first function. We'll return to our project we have been using the past tutorials called FirstProject and go into the main code file. After the Mob/Player and Mob/Monster declarations, we will add some new lines.

Example codes will start to be more condensed in order to show only what is important for that particular example. By now you should be able to understand what you are reading and be able to add the code under the proper type. In this example below, just simply put the code after Mob at the end of your Mob chunk of code in the code file. Or you can just put the code how it is displayed in your project and it will work, it'll just be less organized. If this confuses you any, be sure you check the link at the bottom of this tutorial to see what the final source of this tutorial should look like.

Mob function myFunction() this.setLoc(1, 1)

We now have a function added to our code. All mobs will now have a function called myFunction which they can call from any other function, including event functions. The code inside our new custom function should be familiar from the previous tutorial. This function with its code will sit in our source and can only be called if we manually call it, the engine will never automatically call it like it would with an event function.

So let's call this function. In order to call it, we are going to learn and use a new event function. All Mob type diobs have the onLogin and onLogout event functions. The first is called when a client connects to a mob and the second is called when a client disconnects from a mob. We'll go into what a 'client' is in a later tutorial, but for now, let's add a login event function to our player mob type that calls our new function.

Mob Player onLogin() this.myFunction()

Try to put the onLogin event function under our already defined Mob/Player code. Just below the onNew event function would be ideal. You do not have to, though. So what is happening here is, when a client connects to the mob Mob/Player it calls the onLogin event function, which calls our newly added myFunction function, which will set our player's location to 1,1 on the map. So build and run the code and see that we are at 1,1 at the start of the game instead of 5,5 or 10,10 like our other code. The reason we are at 1,1 instead of 10,10, which we set in onNew is because onNew is called before onLogin, so the login event function has the final say on where we end up. All of this happens so fast that we never see the changes.

Now we know how to create our own function and how to call it, but we can also send values to the function and have the function return values. Change the new myFunction to look like the code below.

Mob function myFunction(pX, pY) this.setLoc(pX, pY) return 'It worked!'

And change the Mob/Player onLogin code to look like the following.

Mob Player onLogin() var mes = this.myFunction(2, 2) alert(mes)

Let's pick apart what is going on here.

In the first example code we are adding new arguments to our function. These are values that can be passed into the function, in our case they are assumed to be our x and y values. These variables can be called anything you want, but our in case we name them pX and pY. The first thing we do in our function is pass our two argument variables into the setLoc function. After that, we use something new called return. What return does is it tells the function to return to the function that called it. In this case we tell it not only to return, but to return with a value, which happens to be a string that reads 'It worked!' in our example. Functions may return one value or no value at all. Once the execution reaches the last line of the function it will return automatically, but if you want to include a value or tell it to return prematurely, then we need to include it. We'll see some other examples of return later.

In the second example code we are calling the actual function. We pass two values into the function, which we saw earlier will be read as the x and y values and we store the value that our myFunction function returns into a local variable called mes. Then we call something new called alert with our mes variable passed into it. Basically what alert does is pop up an alert window with a message in it.

Build and run and an alert saying 'It worked!' should appear on your screen then our player should now be at the location 2,2 once you close the alert.

Now that we know some basics about functions, let's take a look at some of the statements that can be used inside of a function. The most common is the if statement and the other statements that go along with it such as else and else if. An if statement is code that checks to see if something is true and then executes the code under it if that statement is infact true. If the statement is not true, then it will skip the code under the if statement and either continue along or run code in an else or else if statement if one is there. An else if statement will be called if the if statement(s) above it are false and an else will be called if no other if statements were true. An else and else if statement must always be attached to an if statement.

Let's see these statements in action. Change our myFunction code to look like the code below.

Mob function myFunction(pX, pY) if (pX === 2) this.setLoc(pX, pY) else if (pX === 3) this.setLoc(3, 1) else this.setLoc(1, 1) return 'It worked!'

There's a lot going on here, let's go through it line by line. First thing we do is check if pX is equal to 2. The three equal signs there basically say compare the things to the left and right of me and if they are exactly equal to eachother, so if pX holds the number 2 in it, then the statement is true, otherwise the statement is false. You may also use only two equal signs, but three equals is a strict compare and it's good practice to use them. The difference between the two might be covered in a later tutorial.

So, in order for the code under this if statement to be called, the if statement must be true, so this means the only time this if statement's code will be executed is if pX is equal to the number 2. If pX is equal to the number 2 then after the code under the if statement has been called, the execution will skip all the way down to the return code, because there is no reason to call the else codes. But if pX is not equal to 2 then the execution will move to the next statement attached to the if if there is one, and in this case there is. Now, the else if is the same deal, but this time pX must be equal to the number 3 in order for the code under it to be executed. If pX does not equal the number 3 then we head to the else which runs that code no matter what. Basically what the else is saying is if the two above if statements are not true, do this, but don't do this if they are true.

Now, because we pass 2 into our myFunction function as the pX value, our first if statement should always execute, meaning our player's location will be set to pX,pY which is 2,2 in our case. Go ahead and build and run to see that our player appears at 2,2.

So how can we get our other statements to execute? Go to our Mob/Player onLogin code and change the code where we call myFunction to pass in the 3 and 3 values. So replace the 2s with 3s.

Build and run and our player should now appear at the 3,1 location on the map instead of the 3,3 location. This is because in our myFunction code we have the else if statement (which is called because pX does not equal the number 2) that says if pX is equal to the number 3 (which it is) then set our player's location to 3,1. So basically we change the y value from 3 to 1.

Try some values where the x value is not equal to the numbers 2 or 3 and no matter what numbers you put, we should always appear at the location 1,1 because our else basically says that if pX does not equal the number 3 or 2 then set the location to 1,1.

Many things can be put inside of an if statement. So far we have seen how to compare two things to see if they are equal, but we can also check to see if one of the values is either greater than or less than. These checks can be done on numbers or strings. For strings it would be based on alphabeticalization.

Let's change our previous statements to make use of greater than and less than. Change the myFunction function code to look something like the code below.

Mob function myFunction(pX, pY) if (pX > 3) this.setLoc(pX, pY) else if (pX <= 3) this.setLoc(3, 1) else this.setLoc(1, 1) return 'It worked!'

So now our code will first check if pX is greater than the number 3. If this is false then we check to see if pX is less than or equal to the number 3, which obviously it is if it is a number, since it's not greater than 3, but we are learning here. Then the else you would think would never run because the value has to be either greater than, less than, or equal to 3, but in the case that pX is not even a number or string (assuming an error does not occur), then our else will be executed.

Change the numbers in the onLogin event function that we passed into the myFunction to 4 and 5 and then build and run. Our player should appear at 4,5 on the map because the first if statement is executed. Try the values 3 and 4 and our player should appear at 3,1 because of our second if statement.

Now for boolean variable values. A boolean is either equal to true or it is equal to false. Booleans are good for making some type of switch that keeps track of if something is on or off. When you check the boolean in an if statement, it'll execute if the boolean is true and not if it is false. Booleans are pretty common in game development, so expect to be using them often. An example of one being used might be to track if a Mob is stunned or not. Either it is stunned or it is not, true or false.

Let's make use of a boolean and also nest some if statements to show it can be done. Pass a new parameter into the myFunction call code called false. Make your onLogin code look something like this.

Mob Player onLogin() var mes = this.myFunction(4, 5, false) alert(mes)

Then change your myFunction function code to look something like this.

Mob function myFunction(pX, pY, pBool) if (pBool) if (pX > 3) this.setLoc(pX, pY) else if (pX <= 3) this.setLoc(3, 1) else this.setLoc(1, 1) return 'It worked!' else return 'It did not work!'

Build and run and you should now get an alert that says 'It did not work!' because our pBool value is false and our first if statement in our function checks to see if pBool is true. You will also notice that we appear at the location 10,10 because we no longer override our mob's onNew code that sets our location. Go back to where we call myFunction in onLogin and change the false to a true. Build and run again and we should now have our old results back.

If statements can do more than only check if a boolean is true or false, it can check if a variable has a value or not or if it is equal to zero. If a variable is equal to null or 0 or the variable does not exist at all, an if statement will return false for it. In our above example, not only is our if statement checking to see if pBool equals true, it is also checking to see if it has a value at all and is not equal to null or 0. To better understand this, here are a few examples of variables and what an if statement would read them as. Do not include them in your code.

var a = 0 if (a) //false var b = 'a' if (b) //true var c = null if (c) //false var d = 45 if (d) //true

We can also negate things inside of the if statements. A negation is used with an exclamation mark and when you put it infront of something it basically says, whatever the if statement would read this value as, flip it. So a true would be false and a false would be true. Let's change our myFunction function code to make use of this.

Mob function myFunction(pX, pY, pBool) if (!pBool) if (pX !== 3) this.setLoc(pX, pY) else if (pX <= 3) this.setLoc(3, 1) else this.setLoc(1, 1) return 'It worked!' else return 'It did not work!'

So now our first if statement will only execute if pBool is false, because we negate whatever value it happens to have, so in order for us to get the true we need to make the statement run, pBool has to be false. Then inside the first if statement you will notice we changed the first nested if statement to if (pX !== 3). What this means is if pX does not equal the number 3 then execute the if statement. So with the function code we now have, pBool needs to be false and pX has to equal something other than 3 in order for us to move to the location pX,pY which our first nested if statement does.

Finally, we will cover and and ors, which can be used inside of if statements to check multiple things at once. If we want to check if something is equal to something else and another thing is equal to something, we would use the symbols && between each statement. If we wanted to check if something is equal to something else or another thing is equal to something, we would use the symbols || between each statement.

Let's give it a try. Alter your myFunction function code to look like the code below.

Mob function myFunction(pX, pY, pBool) if (!pBool || pX > 3) if (pX !== 3 && pY !== 3) this.setLoc(pX, pY) else if (pX <= 3) this.setLoc(3, 1) else this.setLoc(1, 1) return 'It worked!' else return 'It did not work!'

The myFunction function now calls the first if statement if either pBool is false OR if pX is greater than the number 3. Then if that is true, the next if statement executes if pX does not equal the number 3 AND the variable pY does not equal the number 3 as well. So if both variables are something other than 3, this statement should execute.

So we have now learned how to create our own functions, execute code inside of them, and use statements to check values of things and run different sections of code depending on the results. In the next tutorial we will learn about more statements and other code that we can use inside of functions.

If you followed everything in this tutorial, the source of your project should look something like this. https://vylocity.com/ide/Vylocity/FirstProject3/