Repeat javascript function using multiple variables

Question

I'm not sure how to best explain what I am trying to do, so I'll put together a quick example.

Let's say I have a JavaScript function like this:

function myFunction(){
    doSomething('text string here');
}

I need to repeat this function at a specified interval. I can do that with setTimeout.

However, the text string I need to use is not just one single string, I have three. So my function would kind of look like this:

function myFunction(){
    var stringOne = "My first string";
    var stringTwo = "My second string";
    var stringthree = "My third string";

    doSomething(*string variable name here*);
}

So I need to call the function, let's say every 10 seconds, but each time it runs it needs to use the next text string, in order.

So I need to call:

myFunction, and have it use stringOne.
myFunction, and have it use stringTwo.
myFunction, and have it use stringThree.
And then start back at the first one again.

I could write three separate functions, and tie them together in a loop using setTimeout, but it seems like there should be a better solution.

Use an array!!!

Bergi
– Bergi

2016-10-10 11:54:54 +00:00
Commented Oct 10, 2016 at 11:54 — Bergi
– Bergi, Commented Oct 10, 2016 at 11:54

Nina Scholz · Accepted Answer · 2016-10-10 12:40:52Z

8

You could use a closure for the counter.

function myFunction() {
    var counter = 0,
        fn = function () {
            var array = ["My first string", "My second string", "My third string"];
            console.log(array[counter]);
            counter++;
            counter %= array.length;
        };
        fn();
    return fn;
}
setInterval(myFunction(), 2000);

edited Oct 10, 2016 at 12:40

answered Oct 10, 2016 at 11:57

Nina Scholz

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16 Comments

Sherwin Flight Over a year ago

Out of curiosity, what was the reason for your last code change? The code you had posted previously seems to be working? One further question, how would I get that function to run immediately the first time, and then at the specified interval after that?

Rajesh Dixit Over a year ago

You can use setTimeout with recursion

Rajesh Dixit Over a year ago

@Nina, by any chance have you used array.entries? How do you reset iterator to 0? Sample Fiddle

Nina Scholz Over a year ago

@Rajesh, while i am a great fan of recursions, setInterval works better for fixed invervals than setTimeout and countinuous calls, because it does not uses the stack more than necessary.

Rajesh Dixit Over a year ago

@NinaScholz Where do you get this much knowledge from. Do you take apprentice? But jokes apart, really appreciate you taking time to explain things.

|

JohnnyAW · Accepted Answer · 2016-10-10 11:56:08Z

1

just use a global variable to track the current string:

currentString = 0;

then after each call increase the value and modulo it:

function myFunction(){
    switch(currentString){
    //print the current string
    }

    currentString = (currentString + 1) % 3;
}

answered Oct 10, 2016 at 11:56

JohnnyAW

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1 Comment

JohnnyAW Over a year ago

yeah, true that:)

synthet1c · Accepted Answer · 2016-10-10 12:06:10Z

1

function myFunction(strings){
  var ii = 0
  function iterate(){
    // increment or reset the iterator
    doSomething(strings[ii++ % strings.length])
    // call it again after 1 second (change this)
    setTimeout(iterate, 1000)
  }
  // kick off the iteration of your strings
  iterate()
}

function doSomething(val) {
  console.log(val)
}

// init the iterator with your strings
myFunction([
 'myFunction, and have it use stringOne.',
 'myFunction, and have it use stringTwo.',
 'myFunction, and have it use stringThree.'
])

edited Oct 10, 2016 at 12:06

answered Oct 10, 2016 at 12:01

synthet1c

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3 Comments

JohnnyAW Over a year ago

why would you reinvent modulo?

synthet1c Over a year ago

Cool didn't think of that. Much cleaner

JohnnyAW Over a year ago

you should still use strings.length

adeneo · Accepted Answer · 2016-10-10 12:11:32Z

0

Use a recursive function with incrementing index

(function myFunction(i){
   var arr = ["My first string", "My second string", "My third string"];
   
   setTimeout(function() {
       doSomething( arr[i = i < arr.length ? i : 0] );
       myFunction(++i);
    }, 1000);
})(0);

function doSomething(str) {
    console.log(str)
}

edited Oct 10, 2016 at 12:11

answered Oct 10, 2016 at 11:54

adeneo

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6 Comments

bash0ne Over a year ago

Keep in mind that setTimeout evaluates the passed string inside. Bad for concerning security sides.

adeneo Over a year ago

@bash0ne - why would setTimeout evaluate anything, unless you pass it a string ?

adeneo Over a year ago

@bash0ne - true story how? Do you still think this evaluates the code inside the timeout ?

bash0ne Over a year ago

It is possible to pass the setTimeout function a string in the first parameter which must go through eval(). So yes

adeneo Over a year ago

I'm not passing a string, but an anonymous function, so how is that even remotely relevant ?

|

Redu · Accepted Answer · 2016-10-10 20:28:31Z

0

No need for closures whatsoever; Not mentioned but i have also added a timeout. Just do like this;

var array = ["My first string", "My second string", "My third string"],
      sid;
function runner(i){
  console.log(array[i=i%array.length]); // i hate i growing indefinitely
  sid = setTimeout(_ => runner(++i),2000);
}

runner(0);
setTimeout(_ => clearTimeout(sid),20000);

answered Oct 10, 2016 at 20:28

Redu

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