How to stop a setTimeout loop

Question

I m trying to build a loading indicator with a image sprite and I came up with this function  function setBgPosition        var c   0      var numbers    0  -120  -240  -360  -480  -600  -720       function run            Ext get  common-spinner   setStyle  background-position   numbers c       px 0px            if  c lt numbers length                        setTimeout run  200            else                       setBgPosition                        setTimeout run  200       so the out put is looks like this  http   jsfiddle net TTkre   I had to use setBgPosition    inside else to keep this running in a loop so now my problem is how to stop this loop once I want  load finished

User · Answer

I am not sure  but might be what you want   var c   0  function setBgPosition         var numbers    0  -120  -240  -360  -480  -600  -720       function run                 Ext get  common-spinner   setStyle  background-position   numbers c       px 0px            if  c lt  numbers length                        setTimeout run  200                     else                       Ext get  common-spinner   setStyle  background-position   numbers 0     px 0px                        setTimeout run  200     setBgPosition

User · Answer

I know this is an old question  I d like to post my approach anyway  This way you don t have to handle the 0 trick that T  J  Crowder expained   var keepGoing   true   function myLoop                Do something          if keepGoing            setTimeout myLoop  1000            function startLoop         keepGoing   true      myLoop       function stopLoop         keepGoing   false

User · Answer

As this is tagged with the extjs tag it may be worth looking at the extjs method  http   docs sencha com extjs 6 2 0 classic Ext Function html method-interval  This works much like setInterval  but also takes care of the scope  and allows arguments to be passed too   function setBgPosition         var c   0      var numbers    0  -120  -240  -360  -480  -600  -720       function run            Ext get  common-spinner   setStyle  background-position   numbers c       px 0px            if  c lt numbers length               c 0                      return Ext Function interval run 200      var bgPositionTimer   setBgPosition      when you want to stop you can use clearInterval to stop it  clearInterval bgPositionTimer     An example use case would be   Ext Ajax request       url   example json        success  function response  opts            clearInterval bgPositionTimer               failure  function response  opts            console log  server-side failure with status code     response status           clearInterval bgPositionTimer

User · Answer

SIMPLIEST WAY TO HANDLE TIMEOUT LOOP  function myFunc  terminator   false        if terminator            clearTimeout timeOutVar         else              do something         timeOutVar   setTimeout function   myFunc      1000              myFunc true       - gt  start loop myFunc false       - gt  end loop

User · Answer

You need to use a variable to track  doneness  and then test it on every iteration of the loop  If done    true then return   var done   false   function setBgPosition         if   done   return      var c   0      var numbers    0  -120  -240  -360  -480  -600  -720       function run             if   done   return          Ext get  common-spinner   setStyle  background-position   numbers c       px 0px            if  c lt numbers length                        setTimeout run  200            else                       setBgPosition                        setTimeout run  200      setBgPosition       start the loop  setTimeout  function    done   true     5000       external event to stop loop

User · Answer

var myVar   null   if myVar     clearTimeout myVar    myVar   setTimeout function    alert  Hello       3000

User · Answer

In the top answer  I think the if  timer  statement has been mistakenly placed within the stop   function call  It should instead be placed within the run   function call like if  timer  timer   setTimeout run  200   This prevents future setTimeout statements from being run right after stop   is called  EDIT 2  The top answer is CORRECT for synchronous function calls  If you want to make async function calls  then use mine instead  Given below is an example with what I think is the correct way  feel to correct me if I am wrong since I haven t yet tested this   const runSetTimeoutsAtIntervals        gt        const timeout   1000    setTimeout interval     let runFutureSetTimeouts    Flag that is set based on which cycle continues or ends      const runTimeout   async     gt            await asyncCall      Now even if stopRunSetTimeoutsAtIntervals   is called while this is running  the cycle will stop         if  runFutureSetTimeouts  runFutureSetTimeouts   setTimeout runTimeout  timeout             const stopRunSetTimeoutsAtIntervals        gt            clearTimeout runFutureSetTimeouts          runFutureSetTimeouts   false            runFutureSetTimeouts   setTimeout runTimeout  timeout     Set flag to true and start the cycle     return stopRunSetTimeoutsAtIntervals       You would use the above function like follows  const stopRunSetTimeoutsAtIntervals   runSetTimeoutsAtIntervals      Start cycle stopRunSetTimeoutsAtIntervals      Stop cycle  EDIT 1  This has been tested and works as expected

User · Answer

setTimeout returns a timer handle  which you can use to stop the timeout with clearTimeout   So for instance   function setBgPosition         var c   0          timer   0      var numbers    0  -120  -240  -360  -480  -600  -720       function run             Ext get  common-spinner   setStyle  background-position   numbers c       px 0px            if  c  gt   numbers length                c   0                    timer   setTimeout run  200             timer   setTimeout run  200        return stop       function stop             if  timer                clearTimeout timer               timer   0                So you d use that as   var stop   setBgPosition          later  when you re ready to stop    stop      Note that rather than having setBgPosition call itself again  I ve just had it set c back to 0  Otherwise  this wouldn t work  Also note that I ve used 0 as a handle value for when the timeout isn t pending  0 isn t a valid return value from setTimeout so it makes a handy flag   This is also one of the  few  places I think you d be better off with setInterval rather than setTimeout  setInterval repeats  So   function setBgPosition         var c   0      var numbers    0  -120  -240  -360  -480  -600  -720       function run             Ext get  common-spinner   setStyle  background-position   numbers c       px 0px            if  c  gt   numbers length                c   0                      return setInterval run  200       Used like this   var timer   setBgPosition          later  when you re ready to stop    clearInterval timer     All of the above notwithstanding  I d want to find a way to make setBgPosition stop things itself  by detecting that some completion condition has been satisfied

User · Answer

Try something like this in case you want to stop the loop from inside the function   let timer   setInterval function         Have some code to do something    if   someStopCondition          clearInterval timer        1000      You can also wrap this inside a another function  just make sure you have a timer variable and use clearInterval theTimerVariable  to stop the loop

[javascript] How to stop a setTimeout loop?

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