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1 decade ago by drhayes

I've been trying to blog about my RPG-ish project and the useful stuff I'm writing to get it out the door.

Here's the post about what I'm calling event chains. It's my attempt to stop littering my code with if (timeElapsed > 32) ... type code to provide scripted entity behaviors. There's an associated event chain GitHub repo.

I've also started working on the Sublime Text 2 ImpactJS plugin. It's available through Package Control (you're using Package Control, right?). I tend to update the plugin when it solves an immediate need of mine; if you think feature X would be useful then please file an issue and I'll see what I can do.

1 decade ago by mimik

sublime plugin? Thats awesome!

1 decade ago by bitmapshades

looks like just the thing I need for making scripted events which is awesome!

1 decade ago by taddeimania

I used entity chains in my feb 1gam and I am so glad I did. It made scripted events so much easier. Even optimized certain game state checks to not do calculations every update loop. Your code is clear and has tests. Two thumbs up.

1 decade ago by drhayes

Fantastico! Glad to hear it. Got any suggestions for improvements? I was going to add orUntil which takes a function and interrupts a wait.

1 decade ago by fulvio

@drhayes: EventChain sounds brilliant and I might use it in my game :)

I implemented it in the following way for my player class just to test it out:

update: function() {
    var cx = this.pos.x + 10;
    var cy = this.pos.y;
    var chain = new EventChain()
        .wait(2)            // Wait for 10 seconds.
        .then(function() {  // Then spawn an entity.
  'EntityCoin', cx, cy);
            console.log('Coin spawned at [X: ' + cx + ', Y: ' + cy + ']');
        }).repeat(3)        // Repeat that 3 times.
        .wait(2)            // Wait some more.
        .then(function() {  // Then spawn a different entity.
  'EntityPotion', cx, cy);
            console.log('Potion spawned at [X: ' + cx + ', Y: ' + cy + ']');
    }).repeat();            // Repeat the whole thing forever.


Unfortunately it doesn't seem to be doing anything. Have I missed something?

1 decade ago by drhayes

@fulvio: Yup. Try moving that chain instantiation to your init method.

init: function() {
// ...
this.chain = EventChain()
   // etc...

update: function() {

You'll have to move the cx and cy around, maybe make the chain reference this. I was thinking about changing it to take a reference on creation to set the context to run all those functions in so this works within them; that would make your case much easier.

1 decade ago by fulvio

@drhayes Ahh, that makes much more sense. Thanks, working great now!

1 decade ago by taddeimania

Drhayes: I do have some ideas. Keep your eyes open for a pull request :)

1 decade ago by fulvio

@drhayes: EventChain is bloody impressive. I removed countless amounts of code where I was using delays, stages, spawning, etc all over the place. Now I just throw an EventChain into the init() and trigger it from the update() and BANG!

Props to you for creating that function. Good work!

1 decade ago by drhayes

@taddeimania: Great! It'd be my second pull request ever.

1 decade ago by Neeko

This is almost embarrassing to ask, but how do you include the EventChain in your entity? I understand how to setup the actual chain in the init function, but how do you include the reference to the EventChain function in eventChain.js?

Edit: Solved. From the Impact documentation,

The name of a Module directly corresponds to its file location and name. E.g. the file lib/mygame/my-file.js must define a module with the name '', so it can be properly loaded from other Modules.

eventChain.js defines its module as


so I added eventChain.js to my lib/game/system directory, and in main.js, I added

    // Requiring other modules...

Being global, I can then call EventChain from my player entity, as documented

this.chain = EventChain(this) //etc...

1 decade ago by fulvio

The way I use EventChain is like the following:

    // Requiring other modules...

Then inside your Entity:

text: "foo",
moreText: "bar",
activateEventChain: false,
chain: null,
init: function(x, y, settings) {

    var self = this;
    this.chain = new EventChain()
        .wait(0.5).then(function() {
        }).wait(0.5).then(function() {
update: function() {
    if (this.activateEventChain) {


You should see a "foo" and then "bar" repeat in the console.

1 decade ago by drhayes

I'll update the documentation to include an "Install" section to clear it up, too.

1 decade ago by drhayes

I added a new method called waitForAnimation so you can pause your chain while an animation completes.

You can give it a particular animation or you can just check the current one.

Let me know if it's useful or if you have any questions.

1 decade ago by Neeko

Very nice drhayes, thank you! I actually came across this scenario the other day and used a wait() in the middle of the chain to wait for the animation to play, like so

this.deathEventChain = EventChain(this)
                .then(function() {
                    this.currentAnim = this.anims.dead.rewind();

Of course, hard coding the number of seconds to wait for each type of animation isn't an elegant solution at all. Thanks again for adding waitForAnimation!

1 decade ago by Joncom

Installed the Sublime Text 2 plugin and restarted the app. Don't seem to see any differences, such as auto-completion for or really anything that wasn't already showing up before the install. Anybody got the Sublime Text 2 plugin working?

1 decade ago by drhayes

You shouldn't have to restart. Are you using Package Control to install?

The plugin doesn't immediately change the syntax to ImpactJS for any JS files. I couldn't come up with a way to detect whether or not you're editing an Impact game reliably from the path alone so you have to do it manually.

If you launch the command window (SHIFT+COMMAND+P on a Mac) and type "impactjs" the only choice should be "Set Syntax: ImpactJS". See if that helps.

Incidentally, a recent pull request added the ability to mixin your own EventChain methods.

1 decade ago by stahlmanDesign

@drhayes I just set up Event Chain and it works great.

Another way it can be used is as a mood manager. Imagine a zombie that gets hungry and seeks food for a while, then sleeps... or a normal character that wanders and then changes into a werewolf... then back to normal, etc.

I'll be watching to see if you add any further developments like the mixin.

1 decade ago by drhayes

Thanks! I never would have thought of the mixin myself; that came from a contributor.

You should check out my state machine plugin:

I'm using it for AI in the RPGish thing I'm working on to track aggro, etc... event chains definitely help with the transitions. ( =
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