Javascript switch vs if else if else

Question

Guys I have a couple of questions    Is there a performance difference in JavaScript between a switch statement and an if   else     If so why  Is the behavior of switch and if   else different across browsers   FireFox  IE  Chrome  Opera  Safari    The reason for asking this question is it seems that I get better performance on a switch statement with approx 1000s cases in Firefox      Edited Unfortuantly this is not my code the Javascript is being produced serverside from a compiled library and I have no access to the code  The method that is producing the javascript is called   CreateConditionals string name  string arrayofvalues  string arrayofActions    note arrayofvalues is a comma separated list   what it produces is  function  name   value      if  value     value from array index x           action from array index x          Note  where  name    the name passed into the serverside function  Now I changed the output of the function to be inserted into a TextArea  wrote some JavaScript code to parse through the function  and converted it to a set of case statements    finally I run the function and it runs fine but performance differs in IE and Firefox

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It turns out that if-else if generally faster than switch  http   jsperf com switch-if-else 46

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Workbenching might result some very small differences in some cases but the way of processing is browser dependent anyway so not worth bothering Because of different ways of processing You can t call it a browser if the behavior would be different anyhow

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Pointy s answer suggests the use of an object literal as an alternative to switch or if else  I like this approach too  but the code in the answer creates a new map object every time the dispatch function is called   function dispatch funCode      var map          explode   function           prepExplosive          if  flammable    issueWarning          doExplode                 hibernate   function           if  status       sleeping   return               I can t keep making this stuff up                           var thisFun   map funCode     if  thisFun  thisFun        If map contains a large number of entries  this can create significant overhead  It s better to set up the action map only once and then use the already-created map each time  for example   var actions          explode   function             prepExplosive            if  flammable     issueWarning            doExplode                 hibernate   function             if  status       sleeping    return                 I can t keep making this stuff up                       function dispatch  name         var action   actions name       if  action   action

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If there is a difference  it ll never be large enough to be noticed  N A No  they all function identically    Basically  use whatever makes the code most readable  There are definitely places where one or the other constructs makes for cleaner  more readable and more maintainable  This is far more important that perhaps saving a few nanoseconds in JavaScript code

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The performance difference between a switch and if   else if   else is small  they basically do the same work  One difference between them that may make a difference is that the expression to test is only evaluated once in a switch while it s evaluated for each if  If it s costly to evaluate the expression  doing it one time is of course faster than doing it a hundred times   The difference in implementation of those commands  and all script in general  differs quite a bit between browsers  It s common to see rather big performance differences for the same code in different browsers   As you can hardly performance test all code in all browsers  you should go for the code that fits best for what you are doing  and try to reduce the amount of work done rather than optimising how it s done

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Is there a preformance difference in   Javascript between a switch statement   and an if   else if    else    I don t think so  switch is useful short if you want prevent multiple if-else conditions      Is the behavior of switch and   if   else if   else different across   browsers   FireFox  IE  Chrome  Opera    Safari    Behavior is same across all browsers

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Sometimes it s better to use neither   For example  in a  dispatch  situation  Javascript lets you do things in a completely different way   function dispatch funCode      var map          explode   function           prepExplosive          if  flammable    issueWarning          doExplode                 hibernate   function           if  status       sleeping   return               I can t keep making this stuff up                           var thisFun   map funCode     if  thisFun  thisFun        Setting up multi-way branching by creating an object has a lot of advantages  You can add and remove functionality dynamically  You can create the dispatch table from data  You can examine it programmatically  You can build the handlers with other functions   There s the added overhead of a function call to get to the equivalent of a  case   but the advantage  when there are lots of cases  of a hash lookup to find the function for a particular key

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Answering in generalities    Yes  usually  See More Info Here  Yes  because each has a different JS processing engine  however  in running a test on the site below  the switch always out performed the if  elseif on a large number of iterations    Test site

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Other than syntax  a switch can be implemented using a tree which makes it O log n   while a if else has to be implemented with an O n  procedural approach  More often they are both processed procedurally and the only difference is syntax  and moreover does it really matter -- unless you re statically typing 10k cases of if else anyway

[javascript] Javascript switch vs. if...else if...else

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