Variable inside setInterval(function, var) is not changing / updating with increment

Question

I am building a browser pet raising game. My plan is to use if/else to determine what the HP drop rate should be for the pet. If below a certain hunger / happiness, the HP will drop faster and faster.

I am using a variable setInterval, and the value inside is not update, but the value is updating when printing to the console.

let hp = 100;
let dropHPWeight = 6000;
let dropHPCall = setInterval(dropHP, dropHPWeight);

  function dropHP() {
    hp = (hp % 360) - 1;
    console.log(dropHPWeight);
    dropHPWeight = dropHPWeight + 6000;
  }

Here I am dropping the HP every 6 seconds, and then as a test, I am seeing if it will increase, but it does not.

Where am I going wrong here?

What's "hp" here? And how will this go faster and faster if you keep adding time? And it's always the first interval's time if you only call "setInterval" once. — Dave Newton, Jun 15 '20 at 20:56
`setInterval(dropHP, dropHPWeight)` does not store the actual variable, the `dropHPWaight` variable is being evaluated and it's value (6000) is being passed to `setInterval`. Raising the variable's value will not change the interval. — MrLumie, Jun 15 '20 at 20:59
Does this answer your question? [Changing the interval of SetInterval while it's running](https://stackoverflow.com/questions/1280263/changing-the-interval-of-setinterval-while-its-running) — Heretic Monkey, Jun 15 '20 at 21:06
It's more likely Heritic's reference is what you're looking for, e.g., at the end of the timeout, call `setTimeout` again w/ the same method argument and the new time. Once a `setInterval` is started, it will always have the same interval (that's the point of it). — Dave Newton, Jun 15 '20 at 22:13

score 0 · Answer 1 · answered Jun 15 '20 at 23:37

As some are mentioning in the comments, you cannot change the interval of a setInterval once it has been initiated. You are better off using setTimeout. Like this:

let hp = 100;
let dropHPWait = 6000;

function dropHP() {

  hp = (hp % 360) - 1;
  dropHPWeight = dropHPWait + 6000;

  if (somecondition){
    setTimeout(dropHP, dropHPWait)
  }

}

dropHP()

Now you call dropHP, which changes the interval, and then uses setTimeout to call itself again after the given increment. I stuck the setTimeout inside some conditional, because you don't want it to run forever (so you have to decide at what point you want it to stop running).

Variable inside setInterval(function, var) is not changing / updating with increment

1 Answers1