How to get the nth occurrence in a string

Question

I would like to get the starting position of the 2nd occurrence of ABC with something like this   var string    XYZ 123 ABC 456 ABC 789 ABC   getPosition string   ABC   2     -- gt  16   How would you do it

User · Answer

Because recursion is always the answer   function getPosition input  search  nth  curr  cnt        curr   curr    0      cnt   cnt    0      var index   input indexOf search       if  curr     nth            if   index                return cnt                    else               return -1                      else           if   index                return getPosition input slice index   search length                 search                nth                  curr                cnt   index   search length                     else               return -1

User · Answer

Working off of kennebec s answer  I created a prototype function which will return -1 if the nth occurence is not found rather than 0   String prototype nthIndexOf   function pattern  n        var i   -1       while  n--  amp  amp  i    lt  this length            i   this indexOf pattern  i           if  i  lt  0  break             return i

User · Answer

Here s my solution  which just iterates over the string until n matches have been found   String prototype nthIndexOf   function searchElement  n  fromElement        n   n    0      fromElement   fromElement    0      while  n  gt  0            fromElement   this indexOf searchElement  fromElement           if  fromElement  lt  0                return -1                    --n            fromElement            return fromElement - 1      var string    XYZ 123 ABC 456 ABC 789 ABC   console log string nthIndexOf  ABC   2      gt  gt  16

User · Answer

function getStringReminder str  substr  occ       let index   str indexOf substr      let preindex          let i   1     while  index     -1          preIndex   index        if  occ    i            break                index   str indexOf substr  index   1        i            return preIndex    console log getStringReminder  bcdefgbcdbcd    bcd   3

User · Answer

x000D   x000D  const string    XYZ 123 ABC 456 ABC 789 ABC   x000D   x000D  function getPosition string  subString  index    x000D    return string split subString  index  join subString  length  x000D    x000D   x000D  console log  x000D    getPosition string   ABC   2     -- gt  16 x000D    x000D   x000D   x000D

User · Answer

Using  String indexOf  1   var stringToMatch    XYZ 123 ABC 456 ABC 789 ABC    function yetAnotherGetNthOccurance string  seek  occurance        var index   0  i   1       while  index     -1            index   string indexOf seek  index   1           if  occurance     i               break                    i              if  index     -1            console log  Occurance found in     index     position              else if  index     -1  amp  amp  i     occurance            console log  Occurance not found in     occurance     position              else           console log  Occurance not found             yetAnotherGetNthOccurance stringToMatch   ABC   2       Output  Occurance found in 16 position  yetAnotherGetNthOccurance stringToMatch   ABC   20       Output  Occurance not found in 20 position  yetAnotherGetNthOccurance stringToMatch   ZAB   1      Output  Occurance not found

User · Answer

Using indexOf and Recursion   First check if the nth position passed is greater than the total number of substring occurrences  If passed  recursively go through each index until the nth one is found   var getNthPosition   function str  sub  n        if  n  gt  str split sub  length - 1  return -1      var recursePosition   function n            if  n     0  return str indexOf sub           return str indexOf sub  recursePosition n - 1    1              return recursePosition n

User · Answer

I was playing around with the following code for another question on StackOverflow and thought that it might be appropriate for here   The function printList2 allows the use of a regex and lists all the occurrences in order    printList was an attempt at an earlier solution  but it failed in a number of cases     x000D   x000D   lt html gt  x000D   lt head gt  x000D   lt title gt Checking regex lt  title gt  x000D   lt script gt  x000D  var string1    123xxx5yyy1234ABCxxxabc   x000D  var search1     d    x000D  var search2     d   x000D  var search3    abc   x000D  function printList search    x000D     document writeln   lt p gt Searching using regex      search      printList  lt  p gt     x000D     var list   string1 match search   x000D     if  list    null    x000D        document writeln   lt p gt No matches lt  p gt     x000D        return  x000D       x000D        document writeln   lt p gt     list toString       lt  p gt     x000D        document writeln   lt p gt     typeof list1      lt  p gt     x000D        document writeln   lt p gt     Array isArray list1      lt  p gt     x000D        document writeln   lt p gt     list1     lt  p gt     x000D     var count   list length  x000D     document writeln   lt ul gt     x000D     for  i   0  i  lt  count  i      x000D        document writeln   lt li gt             list i        length     list i  length    x000D              first position     string1 indexOf list i       lt  li gt     x000D       x000D     document writeln   lt  ul gt     x000D    x000D  function printList2 search    x000D     document writeln   lt p gt Searching using regex      search      printList2  lt  p gt     x000D     var index   0  x000D     var partial   string1  x000D     document writeln   lt ol gt     x000D     for  j   0  j  lt  100  j      x000D         var found   partial match search   x000D         if  found    null    x000D               document writeln   lt p gt not found lt  p gt     x000D            break  x000D           x000D         var size   found 0  length  x000D         var loc   partial search search   x000D         var actloc   loc   index  x000D         document writeln   lt li gt     found 0       length     size      first position     actloc   x000D            document writeln        partial          loc   x000D         partial   partial substring loc   size   x000D         index   index   loc   size  x000D         document writeln   lt  li gt     x000D       x000D     document writeln   lt  ol gt     x000D   x000D    x000D   lt  script gt  x000D   lt  head gt  x000D   lt body gt  x000D   lt p gt Original string is  lt script gt document writeln string1   lt  script gt  lt  p gt  x000D   lt script gt  x000D     printList   d  g   x000D     printList2   d     x000D     printList   d g   x000D     printList2   d    x000D     printList  abc g   x000D     printList2  abc    x000D     printList  ABC gi   x000D     printList2  ABC i   x000D   lt  script gt  x000D   lt  body gt  x000D   lt  html gt  x000D   x000D   x000D

User · Answer

You can also use the string indexOf without creating any arrays   The second parameter is the index to start looking for the next match   function nthIndex str  pat  n       var L  str length  i  -1      while n--  amp  amp  i   lt L           i  str indexOf pat  i           if  i  lt  0  break            return i     var s   XYZ 123 ABC 456 ABC 789 ABC    nthIndex s  ABC  3       returned value   Number  24

User · Answer

a simple solution just add string  character and idx  function getCharIdx str char n     let r   0   for  let i   0  i lt str length  i         if  str i      char         r         if  r     n           return i

User · Answer

Shorter way and I think easier  without creating unnecessary strings   const findNthOccurence    string  nth  char    gt      let index   0   for  let i   0  i  lt  nth  i    1        if  index     -1  index   string indexOf char  index   1        return index

User · Answer

This method creates a function that calls for the index of nth occurrences stored in an array  function nthIndexOf search  n         var myArray            for var i   0  i  lt  myString length  i        loop thru string to check for occurrences         if myStr slice i  i   search length      search      if match found                myArray push i     store index of each occurrence                                 return myArray n - 1     first occurrence stored in index 0

[javascript] How to get the nth occurrence in a string?

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