Execute the setInterval function without delay the first time

Question

It s there a way to configure the setInterval method of javascript to execute the method immediately and then executes with the timer

User · Answer

Here s a wrapper to pretty-fy it if you need it    function         var originalSetInterval   window setInterval       window setInterval   function fn  delay  runImmediately            if runImmediately  fn            return originalSetInterval fn  delay                  Set the third argument of setInterval to true and it ll run for the first time immediately after calling setInterval   setInterval function     console log  hello world       5000  true     Or omit the third argument and it will retain its original behaviour   setInterval function     console log  hello world       5000     Some browsers support additional arguments for setInterval which this wrapper doesn t take into account  I think these are rarely used  but keep that in mind if you do need them

User · Answer

You could wrap setInterval   in a function that provides that behavior   function instantGratification  fn  delay         fn        setInterval  fn  delay           then use it like this   instantGratification  function         console log   invoked        3000

User · Answer

There s a problem with immediate asynchronous call of your function  because standard setTimeout setInterval has a minimal timeout about several milliseconds even if you directly set it to 0  It caused by a browser specific work   An example of code with a REAL zero delay wich works in Chrome  Safari  Opera  function setZeroTimeout callback    var channel   new MessageChannel    channel port1 onmessage   callback  channel port2 postMessage          You can find more information here  And after the first manual call you can create an interval with your function

User · Answer

I m not sure if I m understanding you correctly  but you could easily do something like this   setInterval function hello       console log  world      return hello       5000     There s obviously any number of ways of doing this  but that s the most concise way I can think of

User · Answer

Here s a simple version for novices without all the messing around  It just declares the function  calls it  then starts the interval  That s it    x000D   x000D    Declare your function here x000D  function My Function    x000D    console log  foo    x000D        x000D   x000D    Call the function first x000D  My Function    x000D   x000D    Set the interval x000D  var interval   window setInterval  My Function  500    x000D   x000D   x000D

User · Answer

It s simplest to just call the function yourself directly the first time   foo    setInterval foo  delay     However there are good reasons to avoid setInterval - in particular in some circumstances a whole load of setInterval events can arrive immediately after each other without any delay   Another reason is that if you want to stop the loop you have to explicitly call clearInterval which means you have to remember the handle returned from the original setInterval call   So an alternative method is to have foo trigger itself for subsequent calls using setTimeout instead   function foo           do stuff                  and schedule a repeat    setTimeout foo  delay         start the cycle foo      This guarantees that there is at least an interval of delay between calls   It also makes it easier to cancel the loop if required - you just don t call setTimeout when your loop termination condition is reached   Better yet  you can wrap that all up in an immediately invoked function expression which creates the function  which then calls itself again as above  and automatically starts the loop    function foo                 setTimeout foo  delay           which defines the function and starts the cycle all in one go

User · Answer

x000D   x000D     YCombinator x000D  function anonymous fnc    x000D    return function     x000D      fnc apply fnc  arguments   x000D      return fnc  x000D      x000D    x000D   x000D     Invoking the first time  x000D  setInterval anonymous function     x000D    console log  bar    x000D        4000   x000D   x000D     Not invoking the first time  x000D  setInterval anonymous function     x000D    console log  foo    x000D      4000   x000D     Or simple  x000D  setInterval function     x000D    console log  baz    x000D     4000   x000D   x000D   x000D    Ok this is so complex  so  let me put it more simple    x000D   x000D  function hello status         x000D    console log  world     status count   x000D     x000D    return status  x000D    x000D   x000D  setInterval hello  5   1000  hello   count  0      x000D   x000D   x000D

User · Answer

To solve this problem   I run the function a first time after the page has loaded   function foo           window onload   function        foo        window setInterval function         foo        5000

User · Answer

For someone needs to bring the outer this inside as if it s an arrow function    function f         this emit             setTimeout f bind this   1000      bind this       If the above producing garbage bothers you  you can make a closure instead    that   gt         function f             that emit                 setTimeout f  1000                this     Or maybe consider using the  autobind decorator depending on your code

User · Answer

You can set a very small initial delay-time  e g  100  and set it to your desired delay-time within the function    x000D   x000D  var delay   100  x000D   x000D  function foo     x000D    console log  Change initial delay-time to what you want     x000D    delay   12000  x000D    setTimeout foo  delay   x000D    x000D   x000D   x000D

User · Answer

There s a convenient npm package called firstInterval  full disclosure  it s mine    Many of the examples here don t include parameter handling  and changing default behaviors of setInterval in any large project is evil   From the docs   This pattern  setInterval callback  1000  p1  p2   callback p1  p2     is identical to  firstInterval callback  1000  p1  p2     If you re old school in the browser and don t want the dependency  it s an easy cut-and-paste from the code

User · Answer

actually the quickest is to do  interval   setInterval myFunction   45000    this will call myfunction  and then will do it agaian every 45 seconds which is different than doing  interval   setInterval myfunction  45000    which won t call it  but schedule it only

User · Answer

I will suggest calling the functions in the following sequence  var  timer   setInterval foo  delay  params   foo params    You can also pass the  timer to the foo  if you want to clearInterval  timer  on a certain condition  var  timer   setInterval function     foo  timer  params     delay   foo  timer  params

User · Answer

I stumbled upon this question due to the same problem but none of the answers helps if you need to behave exactly like setInterval   but with the only difference that the function is called immediately at the beginning   Here is my solution to this problem   function setIntervalImmediately func  interval      func      return setInterval func  interval       The advantage of this solution    existing code using setInterval can easily be adapted by substitution works in strict mode it works with existing named functions and closures you can still use the return value and pass it to clearInterval   later   Example      create 1 second interval with immediate execution var myInterval   setIntervalImmediately      gt            console log  hello           1000       clear interval after 4 5 seconds setTimeout      gt            clearInterval myInterval          4500     To be cheeky  if you really need to use setInterval then you could also replace the original setInterval  Hence  no change of  code required when adding this before your existing code   var setIntervalOrig   setInterval   setInterval   function func  interval        func        return setIntervalOrig func  interval       Still  all advantages as listed above apply here but no substitution is necessary

[javascript] Execute the setInterval function without delay the first time

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