If you search Google for "text adventure" and open the Developer tools, you get a neat little text adventure game to play, which involves the blue G
finding his friends red o
, yellow o
, blue g
, green l
, and the always quirky red e
.
I started wondering how they did this: They implemented a whole command system without using any external stuff, with only plain JavaScript. And so at once I started digging through the code, immediately stopped because it was obfuscated, and started thinking. The result was this simple trivia quiz (hosted here).
How does this even work?
yes
, no
, north
, moon
, they all don't seem to be anything. If you open the DevTools and run them, you'll just get a Uncaught ReferenceError: yes is not defined
. But that gives us a hint – why don't we define it?
const yes = "yes";
// Later...
yes
// => "yes"
That works perfectly, but we have no way of saying whether it was called. But then, we can use getters.
Quick demo of getters
const obj = {
foo: 'bar',
get foo() {
return 'something entirely different'
}
}
obj.foo //=> 'something entirely different'
We obviously can't use getters on global variables, but we can just set the variables on window and add getters to them:
Object.defineProperty(window, "yes", {get: () => {
// Do something
console.log("Got yes");
return "yes";
}});
yes
// => "yes"
// => "Got yes" (logged to console)
And that's basically it, you can just keep setting variables statically or dynamically, and you basically get a command system!
What are the uses of this? I dunno, all this can be done by using regular functions instead of this. Maybe easter eggs? Maybe for some debugging?
I can't wait to see people writing code like this:
Object.defineProperty(window, "main", {get: () => {...}})
main;
// Wait, is main supposed to be a function or something?
// Linters are gonna be angry...
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