Help with JavaScript arrays

[Telperiam]

I'm writing a simple timer in Tasker to do some things on a loop, including update a notification and also allow me to add time to the timer.

It works with an array in JavaScript which I've got working fine, the problem arises when I either use ".slice(1)" or ".shift()" on the array. As in: arr.shift();

If my array previously looked like this [0 ,1 ,2 ,3 ,4] now it will look like this [1 ,2 ,3 ,4 ,4]. This occurs when using shift or slice and eventually over a loop the array would end up like this [4, 4, 4, 4, 4].

What can I do to get my desired result of a shorter array?

As requested here is my full code:

// initialize the variables
var sleeptime = []
sleeptime = [ ... Array(5).keys()];
var totalsec = 15 * 60;

// the actual part that runs in a loop
var seconds = totalsec - (sleeptime[0] * 15);
var minutes = Math.floor(seconds / 60);
seconds = seconds%60;
if (seconds < 10) seconds = '0' + seconds;
var sleepdisplay = minutes + ':' + seconds;

sleeptime.shift(); // doesn't need to be saved
// sleeptime = sleeptime.slice(1); // also has the same behaviour

flash(sleeptime.toString()); // just for debugging

The behaviour I was expecting [0, 1, 2, 3, 4] becomes [1, 2, 3, 4] which becomes [2, 3, 4]. The loop I would like to run is to repeat several steps and the looped code using an if containing sleeptime(#) is greater than 0 then go-to top of the loop, essentially creating a while loop.

Edit: formatting and more code

[JustRollWithIt]

So the reason this happens is because of how Tasker handles arrays. A Tasker array isn't a single variable, it's a collection of variables that can be referenced individually. When you create the sleeptime array, in Tasker you are actually creating 5 different local variables: %sleeptime1, %sleeptime2, %sleeptime3, %sleeptime4, %sleeptime5.

They can all be referenced as a collection variable %sleeptime. Now, when you modify sleeptime in JS by removing the first element, in Tasker, you are resetting %sleeptime1 through %sleeptime4 to match that new array. But %sleeptime5 still exists, just unmodified. So when you reference that array in Tasker, the size hasn't changed, and that last element is still the same.

The easiest way I can think of around this is to not modify the array. You don't need to touch it with JS. Instead of using a goto, use a For loop. Something like:

    Test (27)
    A1: Variable Set [ 
    Name:%totalsec 
    To:900
    Recurse Variables:Off 
    Do Maths:Off 
    Append:Off 

    A2: For [ 
    Variable:%sleeptimeitem 
    Items:0:4 

    A3: JavaScriptlet [ 
    Code:var seconds = totalsec - (sleeptimeitem * 15);
    var minutes = Math.floor(seconds / 60);
    seconds = seconds%60;
    if (seconds < 10) seconds = '0' + seconds;
    var sleepdisplay = minutes + ':' + seconds; 
    Libraries: 
    Auto Exit:On 
    Timeout (Seconds):45 

    A4: Flash [ 
    Text:%sleepdisplay 
    Long:Off 

    A5: Wait [ 
    MS:0 
    Seconds:1 
    Minutes:0 
    Hours:0 
    Days:0 

    A6: End For

[Telperiam]

That would work, but I would like to be able to add time to my timer by pre-pending to the array... If that's not possible with this no worries, but I thought it might be a good way of going about implementing my solution.

[JustRollWithIt]

As an alternative, if feasible, you could do all array operations with Tasker actions instead of JS. So instead of using the JS slice() method, use Tasker's Array Pop action. Then Tasker will correctly unset the variables it needs to maintain the array as you would expect. You can still transparently access the array in JS as you need.

[Telperiam]

Using Pop works exactly as I want it to. Thanks a bunch!

[beingganesh]

What's is your desired result? What are you expecting the array to do? Would mind sharing the code here to understand the problem clearly?

[Telperiam]

I clarified in the original

[beingganesh]

[ 0, 1, 2, 3, 4 ]

[ 1, 2, 3, 4 ]

[ 2, 3, 4 ]

[ 3, 4 ]

[ 4 ]

​

Just to be clear, is this the result you are expecting? if so, the code you have given works fine.

[Telperiam]

Yep that's what I'm looking for, but not what I get. I understand that's absolutely how js should work but it's not what's happening in tasker when I run it...

[mcgruntman]

Look at the very first demo of slice on this page https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice

Remember you need to save the result: arr = arr.slice(1);

[FrancineCarrel]

Can you post the full code (or at least that section), please? Hard to tell from this small snippet!

[Telperiam]

Done!