setTimeout in for-loop does not print consecutive values

Question

I have this script   for  var i   1  i  lt   2  i          setTimeout function     alert i     100       But 3 is alerted both times  instead of 1 then 2   Is there a way to pass i  without writing the function as a string

User · Answer

You could use bind method  for  var i   1  j   1  i  lt   3  i    j          setTimeout function             alert this         bind i   j   100

User · Answer

the real solution is here  but you need to be familiar with PHP programing language  you must mix PHP and JAVASCRIPT orders in order to reach to your purpose   pay attention to this     lt  php  for  i 1  i lt  3  i     echo   lt script language  javascript   gt  setTimeout function   alert     i       3000      lt  script gt        gt     It exactly does what you want  but be careful about how to make ralation between  PHP variables and JAVASCRIPT ones

User · Answer

I had the same problem once this is how I solved it   Suppose I want 12 delays with an interval of 2 secs      function animate i            myVar setTimeout function                alert i               if i  12                 clearTimeout myVar                 return                           animate i 1             2000             var i 1    i is the start point 1 to 12 that is     animate i     1 2 3 4  12 will be alerted with 2 sec delay

User · Answer

Well  another working solution based on Cody s answer but a little more general can be something like this   function timedAlert msg  timing       setTimeout function            alert msg              timing      function yourFunction time  counter       for  var i   1  i  lt   counter  i              var msg   i  timing   i   time   1000    this is in seconds         timedAlert  msg  timing             yourFunction timeInSeconds  counter      well here are the values of your choice

User · Answer

This s Because    The timeout function callbacks are all running well after the completion of the loop  In fact  as timers go  even if it was setTimeout     0  on each iteration  all those function callbacks would still run strictly after the completion of the loop  that s why 3 was reflected  all two of those functions  though they are defined separately in each loop iteration  are closed over the same shared global scope  which has  in fact  only one i in it    the Solution s declaring a single scope for each iteration by using a self-function executed anonymous one or better IIFE  and having a copy of i in it  like this   for  var i   1  i  lt   2  i             function              var j   i           setTimeout function     console log j     100                    the cleaner one would be  for  var i   1  i  lt   2  i             function i              setTimeout function     console log i     100            i        The use of an IIFE self-executed function  inside each iteration created a new scope for each iteration  which gave our timeout function callbacks the opportunity to close over a new scope for each iteration  one which had a variable with the right per-iteration value in it for us to access

User · Answer

You can use the extra arguments to setTimeout to pass parameters to the callback function   for  var i   1  i  lt   2  i          setTimeout function j    alert j     100  i       Note  This doesn t work on IE9 and below browsers

User · Answer

ANSWER   I m using it for an animation for adding items to a cart - a cart icon floats to the cart area from the product  add  button  when clicked   function addCartItem opts        for  var i 0  i lt opts qty  i              setTimeout function                 console log  ADDED ONE                1000 i              NOTE the duration is in unit times n epocs   So starting at the the click moment  the animations start epoc  of EACH animation  is the product of each one-second-unit multiplied by the number of items   epoc  https   en wikipedia org wiki Epoch  reference date   Hope this helps

User · Answer

The function argument to setTimeout is closing over the loop variable  The loop finishes before the first timeout and displays the current value of i  which is 3   Because JavaScript variables only have function scope  the solution is to pass the loop variable to a function that sets the timeout  You can declare and call such a function like this   for  var i   1  i  lt   2  i           function  x            setTimeout function      alert x      100          i

User · Answer

You can use an immediately-invoked function expression  IIFE  to create a closure around setTimeout    x000D   x000D  for  var i   1  i  lt   3  i      x000D       function index    x000D          setTimeout function     alert index      i   1000   x000D         i   x000D    x000D   x000D   x000D

User · Answer

You have to arrange for a distinct copy of  i  to be present for each of the timeout functions   function doSetTimeout i      setTimeout function     alert i      100      for  var i   1  i  lt   2    i    doSetTimeout i     If you don t do something like this  and there are other variations on this same idea   then each of the timer handler functions will share the same variable  i    When the loop is finished  what s the value of  i    It s 3   By using an intermediating function  a copy of the value of the variable is made  Since the timeout handler is created in the context of that copy  it has its own private  i  to use    edit  mdash  there have been a couple of comments over time in which some confusion was evident over the fact that setting up a few timeouts causes the handlers to all fire at the same time  It s important to understand that the process of setting up the timer  mdash  the calls to setTimeout    mdash  take almost no time at all  That is  telling the system   Please call this function after 1000 milliseconds  will return almost immediately  as the process of installing the timeout request in the timer queue is very fast   Thus  if a succession of timeout requests is made  as is the case in the code in the OP and in my answer  and the time delay value is the same for each one  then once that amount of time has elapsed all the timer handlers will be called one after another in rapid succession   If what you need is for the handlers to be called at intervals  you can either use setInterval    which is called exactly like setTimeout   but which will fire more than once after repeated delays of the requested amount  or instead you can establish the timeouts and multiply the time value by your iteration counter  That is  to modify my example code   function doScaledTimeout i      setTimeout function         alert i        i   5000        With a 100 millisecond timeout  the effect won t be very obvious  so I bumped the number up to 5000   The value of i is multiplied by the base delay value  so calling that 5 times in a loop will result in delays of 5 seconds  10 seconds  15 seconds  20 seconds  and 25 seconds   Update  Here in 2018  there is a simpler alternative  With the new ability to declare variables in scopes more narrow than functions  the original code would work if so modified   for  let i   1  i  lt   2  i          setTimeout function     alert i     100       The let declaration  unlike var  will itself cause there to be a distinct i for each iteration of the loop

[javascript] setTimeout in for-loop does not print consecutive values

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