is the operator less performant than StringBuffer append

Question

On my team  we usually do string concatentation like this   var url      some dynamically generated URL var sb   new StringBuffer    sb append   lt a href     append url  append    gt click here lt  a gt       Obviously the following is much more readable   var url      some dynamically generated URL var sb     lt a href      url      gt click here lt  a gt      But the JS experts claim that the   operator is less performant than StringBuffer append    Is this really true

User · Answer

Try this   var s      lt a href     url     gt click here lt  a gt    join

User · Answer

Agreed with Michael Haren   Also consider the use of arrays and join if performance is indeed an issue   var buffer      lt a href     url     gt click here lt  a gt     buffer push  More stuff    alert buffer join

User · Answer

Internet Explorer is the only browser which really suffers from this in today s world    Versions 5  6  and 7 were dog slow   8 does not show the same degradation    What s more  IE gets slower and slower the longer your string is   If you have long strings to concatenate then definitely use an array join technique    Or some StringBuffer wrapper around this  for readability    But if your strings are short don t bother

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In the words of Knuth   premature optimization is the root of all evil   The small defference either way will most likely not have much of an effect in the end  I d choose the more readable one

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Like already some users have noted  This is irrelevant for small strings   And new JavaScript engines in Firefox  Safari or Google Chrome optimize so    lt a href      url      gt click here lt  a gt      is as fast as     lt a href     url     gt click here lt  a gt    join

User · Answer

Yes  according to the usual benchmarks  E G   http   mckoss com jscript SpeedTrial htm   But for the small strings  this is irrelevant  You will only care about performances on very large strings  What s more  in most JS script  the bottle neck is rarely on the string manipulations since there is not enough of it   You d better watch the DOM manipulation

User · Answer

Yes it s true but you shouldn t care  Go with the one that s easier to read  If you have to benchmark your app  then focus on the bottlenecks    I would guess that string concatenation isn t going to be your bottleneck

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I like to use functional style  such as   function href url txt      return   lt a href     url     gt    txt    lt  a gt      function li txt      return   lt li gt    txt    lt  li gt      function ul arr      return   lt ul gt     arr map li  join         lt  ul gt      document write    ul              href  http   url1   link1          href  http   url2   link2          href  http   url3   link3                 This style looks readable and transparent   It leads to the creation of utilities which reduces repetition in code   This also tends to use intermediate strings automatically

User · Answer

Your example is not a good one in that it is very unlikely that the performance will be signficantly different   In your example readability should trump performance because the performance gain of one vs the other is negligable   The benefits of an array  StringBuffer  are only apparent when you are doing many concatentations   Even then your mileage can very depending on your browser   Here is a detailed performance analysis that shows performance using all the different JavaScript concatenation methods across many different browsers  String Performance an Analysis    More  Ajaxian    String Performance in IE  Array join vs    continued

User · Answer

The easier to read method saves humans perceptible amounts of time when looking at the code  whereas the  faster  method only wastes imperceptible and likely negligible amounts of time when people are browsing the page   I know this post is lame  but I accidentally posted something entirely different thinking this was a different thread and I don t know how to delete posts  My bad

User · Answer

JavaScript doesn t have a native StringBuffer object  so I m assuming this is from a library you are using  or a feature of an unusual host environment  i e  not a browser    I doubt a library  written in JS  would produce anything faster  although a native StringBuffer object might  The definitive answer can be found with a profiler  if you are running in a browser then Firebug will provide you with a profiler for the JS engine found in Firefox

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As far I know  every concatenation implies a memory reallocation  So the problem is not the operator used to do it  the solution is to reduce the number of concatenations  For example do the concatenations outside of the iteration structures when you can

User · Answer

It is pretty easy to set up a quick benchmark and check out Javascript performance variations using jspref com  Which probably wasn t around when this question was asked  But for people stumbling on this question they should take alook at the site   I did a quick test of various methods of concatenation at http   jsperf com string-concat-methods-test

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