What is the difference between substr and substring

Question

What is the difference between  alert  abc  substr 0 2      and  alert  abc  substring 0 2      They both seem to output    ab

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substring startIndex  endIndex not included    substr startIndex  how many characters   const string    JavaScript    console log  substring 1 2    string substring 1 2       a console log  substr 1 2    string substr 1 2       av

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let str    quot Hello World quot   console log str substring 1  3       el - gt  Excludes the last index console log str substr 1  3       ell - gt  Includes the last index

User · Answer

The difference is second parameter  Their second parameters  while both numbers  are expecting two different things   When using substring the second parameter is the first index not to include   var s    string   s substring 1  3      would return  tr   var s    another example   s substring 3  7      would return  ther    When using substr the second parameter is the number of characters to include in the substring   var s    string   s substr 1  3      would return  tri   var s    another example   s substr 3  7      would return  ther ex

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The big difference is  substr   is a deprecated method that can still be used  but should be used with caution because they are expected to be removed entirely sometime in the future  You should work to remove their use from your code  And the substring   method succeeded and specified the former one

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substring  MDN  takes parameters as  from  to   substr  MDN  takes parameters as  from  length   Update  MDN considers substr legacy  alert  quot abc quot  substr 1 2       returns  quot bc quot  alert  quot abc quot  substring 1 2       returns  quot b quot   You can remember substring  with an i  takes indices  as does yet another string extraction method  slice  with an i   When starting from 0 you can use either method

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The main difference is that  substr   allows you to specify the maximum length to return   substring   allows you to specify the indices and the second argument is NOT inclusive  There are some additional subtleties between substr   and substring   such as the handling of equal arguments and negative arguments  Also note substring   and slice   are similar but not always the same           length vs indices       string  substring 2 4        ri     start  end  indices   second value is NOT inclusive      string  substr 2 4           ring   start  length  length is the maximum length to return      string  slice 2 4            ri     start  end  indices   second value is NOT inclusive          watch out for substring swap       string  substring 3 2        r      swaps the larger and the smaller number       string  substr 3 2           in       string  slice 3 2                   just returns              negative second argument       string  substring 2 -4       st     converts negative numbers to 0  then swaps first and second position       string  substr 2 -4                 string  slice 2 -4                      negative first argument       string  substring -3         string               string  substr -3            ing    read from end of string       string  slice -3             ing

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The difference is in the second argument  The second argument to substring is the index to stop at  but not include   but the second argument to substr is the maximum length to return  Links  https   developer mozilla org en-US docs Web JavaScript Reference Global Objects String substr https   developer mozilla org en-US docs Web JavaScript Reference Global Objects String substring

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substring     It has 2 parameters  start  and  end      start parameter is required and specifies the position where to start the extraction    end parameter is optional and specifies the position    where the extraction should end    If the end parameter is not specified  all the characters from the start position till the end of the string are extracted     x000D   x000D  var str    Substring Example   x000D  var result   str substring 0  10   x000D  alert result   x000D   x000D  Output   Substring x000D   x000D   x000D    If the value of start parameter is greater than the value of the end parameter  this method will swap the two arguments  This means start will be used as end and end will be used as start    x000D   x000D  var str    Substring Example   x000D  var result   str substring 10  0   x000D  alert result   x000D   x000D  Output   Substring x000D   x000D   x000D    substr    It has 2 parameters  start  and  count      start parameter is required and specifies the position where to start the extraction  count parameter is optional and specifies the number of characters to extract     x000D   x000D  var str    Substr Example   x000D  var result   str substr 0  10   x000D  alert result   x000D   x000D   x000D  Output   Substr Exa x000D   x000D   x000D    If the count parameter is not specified  all the characters from the start position till the end of the string are extracted  If count is 0 or negative  an empty string is returned    x000D   x000D  var str    Substr Example   x000D  var result   str substr 11   x000D  alert result   x000D   x000D  Output   ple x000D   x000D   x000D

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Another gotcha I recently came across is that in IE 8   abcd  substr -1  erroneously returns  abcd   whereas Firefox 3 6 returns  d  as it should  slice works correctly on both   More on this topic can be found here

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As hinted at in yatima2975 s answer  there is an additional difference   substr   accepts a negative starting position as an offset from the end of the string   substring   does not   From MDN      If start is negative  substr   uses it as a character index from the   end of the string    So to sum up the functional differences   substring begin-offset  end-offset-exclusive  where begin-offset is 0 or greater  substr begin-offset  length  where begin-offset may also be negative

[javascript] What is the difference between substr and substring?

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