clearInterval not working

Question

Possible Duplicate    JS - How to clear interval after using setInterval         I have a function that changes the font-family of some text every 500 ms using setInterval  I made it just to practice JavaScript   The function is called by clicking on an  on  button and the interval is supposed to be cleared using a separate button   off   However  the  off  button doesn t actually clear the interval  it just continues  I suspect that this has something to do with scope but I m not sure how to write it any other way  Also  I don t want to do this with jQuery because  after all  I m doing it to learn    lt body gt   lt p gt  lt span id  go  class  georgia  gt go lt  span gt  Italian lt  p gt   lt p gt       lt button id  on  type  button  value  turn on  gt turn on lt  button gt       lt button id  off  type  button  value  turn off  gt turn off lt  button gt   lt  p gt    lt script gt  var text   document getElementById  go    var on   document getElementById  on    var off   document getElementById  off     var fontChange   function         switch text className            case  georgia               text className    arial               break          case  arial               text className    courierNew               break          case  courierNew               text className    georgia               break                  on onclick   function         setInterval fontChange  500       off onclick   function         clearInterval fontChange        lt  script gt   lt  body gt

User · Answer

The setInterval function returns an integer value  which is the id of the  timer instance  that you ve created   It is this integer value that you need to pass to clearInterval  e g   var timerID   setInterval fontChange 500     and later  clearInterval timerID

User · Answer

setInterval returns an ID which you then use to clear the interval    var intervalId  on onclick   function         if  intervalId            clearInterval intervalId             intervalId   setInterval fontChange  500       off onclick   function         clearInterval intervalId

User · Answer

i think you should do   var myInterval on onclick   function         myInterval setInterval fontChange  500       off onclick   function         clearInterval myInterval

User · Answer

The setInterval method returns an interval ID that you need to pass to clearInterval in order to clear the interval  You re passing a function  which won t work  Here s an example of a working setInterval clearInterval  var interval id   setInterval myMethod 500   clearInterval interval id

User · Answer

You re using clearInterval incorrectly   This is the proper use   Set the timer with  var name   setInterval fontChange  500     and then  clearInterval var name

User · Answer

There are errors in your functions  but the first thing you should do  is to set the body tag correctly    lt body gt   lt p gt  lt span id  go  class  georgia  gt go lt  span gt  Italian lt  p gt   lt p gt       lt button id  on  type  button  value  turn on  gt turn on lt  button gt       lt button id  off  type  button  value  turn off  gt turn off lt  button gt   lt  p gt   lt  body gt    lt script gt      lt  script gt    The problem sometimes may be  that you call  var text  and the other vars only once  when the script starts  If you make changements to the DOM  this static solution may be harmful   So you could try this  this is more flexible approach and using function parameters  so you can call the functions on any element     lt body gt   lt p gt  lt span id  go  class  georgia  gt go lt  span gt  Italian lt  p gt   lt p gt       lt button type  button  value  turn on           onclick turnOn  go   gt turn on lt  button gt       lt button type  button  value  turn off           onclick turnOff   gt turn off lt  button gt   lt  p gt   lt  body gt    lt script type  text JavaScript  gt  var interval   var turnOn   function elementId       interval   setInterval function   fontChange elementId     500       var turnOff   function        clearInterval interval       var fontChange   function elementId        var text   document getElementById elementId       switch text className            case  georgia               text className    arial               break          case  arial               text className    courierNew               break          case  courierNew               text className    georgia               break                  lt  script gt    You don t need this anymore  so delete it   var text   document getElementById  go    var on   document getElementById  on    var off   document getElementById  off      This is dynamic code  meaning JS code which runs generic and doesn t adress elements directly  I like this approach more than defining an own function for every div element

[javascript] clearInterval() not working

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