split string only on first instance of specified character

Question

In my code I split a string based on   and grab the second item in the array   var element     this  attr  class    var field   element split      1     Takes good luck and provides me with luck  Works great   But  now I have a class that looks like good luck buddy  How do I get my javascript to ignore the second   and give me luck buddy   I found this var field   element split new char           2   in a c  stackoverflow answer but it doesn t work  I tried it over at jsFiddle

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Javascript s String split unfortunately has no way of limiting the actual number of splits  It has a second argument that specifies how many of the actual split items are returned  which isn t useful in your case  The solution would be to split the string  shift the first item off  then rejoin the remaining items    var element     this  attr  class    var parts   element split        parts shift       removes the first item from the array var field   parts join

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Replace the first instance with a unique placeholder then split from there    good luck buddy  replace        amp    split   amp       good   luck buddy     This is more useful when both sides of the split are needed

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With help of destructuring assignment it can be more readable   let  first     rest     good luck buddy  split      rest   rest join

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For beginner like me who are not used to Regular Expression  this workaround solution worked          var field    Good Luck Buddy      var newString   field slice  field indexOf      1      slice   method extracts a part of a string and returns a new string and indexOf   method returns the position of the first found occurrence of a specified value in a string

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Nowadays String prototype split does indeed allow you to limit the number of splits      str split  separator   limit                  limit Optional      A non-negative integer limiting the number of splits  If provided  splits the string at each occurrence of the specified separator  but stops when limit entries have been placed in the array  Any leftover text is not included in the array at all       The array may contain fewer entries than limit if the end of the string is reached before the limit is reached    If limit is 0  no splitting is performed    caveat  It might not work the way you expect  I was hoping it would just ignore the rest of the delimiters  but instead  when it reaches the limit  it splits the remaining string again  omitting the part after the split from the return results   let str    A B C D E  const limit 2   str split      2  limit 2  2     A    B   const limit 3   str split      3  limit 3  3     A    B    C     I was hoping for   let str    A B C D E  const limit 2   str split      2  limit 2  2     A    B C D E   const limit 3   str split      3  limit 3  3     A    B    C D E

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A simple ES6 way to get both the first key and remaining parts in a string would be   const  key     rest     quot good luck buddy quot  split       const value   rest join       console log key  value     good  luck buddy

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What do you need regular expressions and arrays for   myString   myString substring myString indexOf      1     x000D   x000D  var myString   hello there how are you  x000D  myString   myString substring myString indexOf      1  x000D  console log myString  x000D   x000D   x000D

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Use capturing parentheses    good luck buddy  split          1   luck buddy    They are defined as     If separator contains capturing parentheses  matched results are   returned in the array    So in this case we want to split at      i e  split separator being a sub string starting with    but also let the result contain some part of our separator  i e  everything after      In this example our separator  matching        is  luck buddy and the captured group  within the separator  is lucky buddy  Without the capturing parenthesis the luck buddy  matching     would ve not been included in the result array as it is the case with simple split that separators are not included in the result

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Mark F s solution is awesome but it s not supported by old browsers  Kennebec s solution is awesome and supported by old browsers but doesn t support regex   So  if you re looking for a solution that splits your string only once  that is supported by old browsers and supports regex  here s my solution    x000D   x000D  String prototype splitOnce   function regex  x000D    x000D      var match   this match regex   x000D      if match  x000D        x000D          var match i   this indexOf match 0    x000D           x000D          return  this substring 0  match i   x000D          this substring match i   match 0  length    x000D        x000D      else x000D        return  this         x000D    x000D   x000D  var str    something     another thing   again   x000D   x000D  alert str splitOnce        1    x000D   x000D   x000D

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I avoid RegExp at all costs  Here is another thing you can do    good luck buddy  split      slice 1  join

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Here s one RegExp that does the trick    good luck buddy    split          1     First it forces the match to start from the start with the      Then it matches any number of characters which are not      in other words all characters before the first       The     means a minimal number of chars  that make the whole pattern match are  matched by the       because it is followed by      which is then included in the match  as its last character    Therefore this split   uses such a matching part as its  splitter  and removes it from the results  So it removes everything up till and including the first     and  gives you the rest as the 2nd element of  the result  The first element is    representing  the part before the matched part  It is    because the match starts from the beginning   There are other RegExps that work as well like         given by Chandu in a previous answer    The         has the benefit that you  can understand what  it does without  having to know about the special role  capturing groups play with replace

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Use the string replace   method with a regex    x000D   x000D  var result    good luck buddy  replace              x000D  console log result   x000D   x000D   x000D    This regex matches 0 or more characters before the first    and the   itself  The match is then replaced by an empty string

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Non-regex solution I ran some benchmarks  and this solution won hugely 1 str slice str indexOf delim    delim length      as function function gobbleStart str  delim        return str slice str indexOf delim    delim length         as polyfill String prototype gobbleStart   function delim        return this slice this indexOf delim    delim length       Performance comparison with other solutions The only close contender was the same line of code  except using substr instead of slice  Other solutions I tried involving split or RegExps took a big performance hit and were about 2 orders of magnitude slower  Using join on the results of split  of course  adds an additional performance penalty  Why are they slower  Any time a new object or array has to be created  JS has to request a chunk of memory from the OS  This process is very slow  Here are some general guidelines  in case you are chasing benchmarks   New dynamic memory allocations for objects    or arrays     like the one that split creates  will cost a lot in performance  RegExp searches are more complicated and therefore slower than string searches  If you already have an array  destructuring arrays is about as fast as explicitly indexing them  and looks awesome   Removing beyond the first instance Here s a solution that will slice up to and including the nth instance  It s not quite as fast  but on the OP s question  gobble element       1  is still  gt 2x faster than a RegExp or split solution and can do more      gobble   given a positive  non-zero  limit   deletes characters from the beginning of  haystack  until  needle  has been encountered and deleted  limit  times or no more instances of  needle  exist  then it returns what remains  If  limit  is zero or negative  delete from the beginning only until  - limit   occurrences or less of  needle  remain     function gobble haystack  needle  limit   0      let remain   limit    if  limit  lt   0       set remain to count of delim - num to leave     let i   0      while  i  lt  haystack length          const found   haystack indexOf needle  i         if  found     -1            break                remain          i   found   needle length               let i   0    while  remain  gt  0        const found   haystack indexOf needle  i       if  found     -1          break            remain--      i   found   needle length        return haystack slice i      With the above definition  gobble  path to file txt        would give the name of the file  and gobble  prefix category item        1  would remove the prefix like the first solution in this answer    Tests were run in Chrome 70 0 3538 110 on macOSX 10 14

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I need the two parts of string  so  regex lookbehind help me with this    x000D   x000D  const full name    Maria do Bairro   x000D  const  first name  last name    full name split     lt              x000D  console log first name   x000D  console log last name   x000D   x000D   x000D

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This should be quite fast function splitOnFirst  str  sep      const index   str indexOf sep     return index  lt  0    str     str slice 0  index   str slice index   sep length

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This solution worked for me  var str    good luck buddy   var index   str indexOf       var arr    str slice 0  index   str slice index   1       arr 0     good    arr 1     luck buddy    OR  var str    good luck buddy   var index   str indexOf       var  first  second     str slice 0  index   str slice index   1       first    good    second    luck buddy

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This worked for me on Chrome   FF    foo bar beer  split            1      bar beer   foo    split            1          foo   split            1         foo  split            1     undefined   If you also need the key try this    foo bar beer  split                 Array        foo    bar beer     foo    split                        foo          foo   split                        foo         foo  split                    foo        0    ignored  holds the string when there s no    empty otherwise     1    hold the key  if any     2    hold the value  if any

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You can use the regular expression like   var arr   element split             You can use the second parameter which specifies the limit of the split  i e       var field   element split      1  1

[javascript] split string only on first instance of specified character

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