What is the difference between String slice and String substring

Question

Does anyone know what the difference is between these two methods   String prototype slice String prototype substring

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Note  if you re in a hurry  and or looking for short answer scroll to the bottom of the answer  and read the last two lines if Not in a hurry read the whole thing let me start by stating the facts   Syntax  string slice start end  string substr start length  string substring start end  Note  1  slice    substring    What it does  The slice   method extracts parts of a string and returns the extracted parts in a new string  The substr   method extracts parts of a string  beginning at the character at the specified position  and returns the specified number of characters  The substring   method extracts parts of a string and returns the extracted parts in a new string  Note  2 slice    substring    Changes the Original String  slice   Doesn t substr   Doesn t substring   Doesn t Note  3 slice    substring    Using Negative Numbers as an Argument  slice   selects characters starting from the end of the string substr  selects characters starting from the end of the string substring   Doesn t Perform Note  3 slice    substr    if the First Argument is Greater than the Second  slice   Doesn t Perform substr   since the Second Argument is NOT a position  but length value  it will perform as usual  with no problems substring   will swap the two arguments  and perform as usual  the First Argument  slice   Required  indicates  Starting Index substr   Required  indicates  Starting Index substring   Required  indicates  Starting Index Note  4 slice    substr    substring    the Second Argument  slice   Optional  The position  up to  but not including  where to end the extraction substr   Optional  The number of characters to extract substring   Optional  The position  up to  but not including  where to end the extraction Note  5 slice    substring    What if the Second Argument is Omitted  slice   selects all characters from the start-position to the end of the string substr   selects all characters from the start-position to the end of the string substring   selects all characters from the start-position to the end of the string Note  6 slice    substr    substring    so  you can say that there s a difference between slice   and substr    while substring   is basically a copy of slice     in Summary  if you know the index the position  on which you ll stop  but NOT include   Use slice   if you know the length of characters to be extracted use substr

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The only difference between slice and substring method is of arguments  Both take two arguments e g  start from and end to   You cannot pass a negative value as first argument for substring method but for slice method to traverse it from end   Slice method argument details   REF   http   www thesstech com javascript string slice method  Arguments  start index Index from where slice should begin  If value is provided in negative it means start from last  e g  -1 for last character  end index Index after end of slice  If not provided slice will be taken from start index to end of string  In case of negative value index will be measured from end of string   Substring method argument details   REF  http   www thesstech com javascript string substring method  Arguments  from It should be a non negative integer to specify index from where sub-string should start  to An optional non negative integer to provide index before which sub-string should be finished

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slice   works like substring   with a few different behaviors   Syntax  string slice start  stop   Syntax  string substring start  stop     What they have in common    If start equals stop  returns an empty string If stop is omitted  extracts characters to the end of the string If either argument is greater than the string s length  the string s length will be used instead    Distinctions of substring      If start  gt  stop  then substring will swap those 2 arguments  If either argument is negative or is NaN  it is treated as if it were 0    Distinctions of slice      If start  gt  stop  slice   will return the empty string       If start is negative  sets char from the end of string  exactly like substr   in Firefox  This behavior is observed in both Firefox and IE  If stop is negative  sets stop to  string length     Math abs stop   original value   except bounded at 0  thus  Math max 0  string length   stop   as covered in the ECMA specification    Source  Rudimentary Art of Programming  amp  Development  Javascript  substr   v s  substring

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For slice start  stop   if stop is negative  stop will be set to   string length     Math abs stop    rather than   string length     1     Math abs stop

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substr  It s providing us to fetch part of the string based on specified index  syntax of substr-    string substr start end     start - start index tells where the fetching start     end - end index tells upto where string fetches  It s optional   slice  It s providing to fetch part of the string based on the specified index  It s allows us to specify positive and index  syntax of slice - string slice start end     start - start index tells where the fetching start It s     end - end index tells upto where string fetches  It s optional    In  splice  both start and end index helps to take positive and negative index   sample code for  slice  in string  var str  Javascript   console log str slice -5 -1     output  crip   sample code for  substring  in string  var str  Javascript   console log str substring 1 5     output  avas     Note  negative indexing starts at the end of the string

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The difference between substring and slice - is how they work with negative and overlooking lines abroad arguments   substring  start  end   Negative arguments are interpreted as zero  Too large values   are truncated to the length of the string         alert    testme   substring  -2        testme   -2 becomes 0  Furthermore  if start   end  the arguments are interchanged  i e  plot line returns between the start and end   alert    testme   substring  4  -1        test     -1 Becomes 0 - gt  got substring  4  0     4 gt  0  so that the arguments are swapped - gt  substring  0  4     test    slice  Negative values   are measured from the end of the line   alert    testme   slice  -2        me   from the end position 2 alert    testme   slice  1  -1        estm   from the first position to the one at the end    It is much more convenient than the strange logic substring   A negative value of the first parameter to substr supported in all browsers except IE8-   If the choice of one of these three methods  for use in most situations - it will be slice  negative arguments and it maintains and operates most obvious

User · Answer

Ben Nadel has written a good article about this  he points out the difference in the parameters to these functions  String slice  begin    end     String substring  from    to     String substr  start    length      He also points out that if the parameters to slice are negative  they reference the string from the end  Substring and substr doesn t  Here is his article about this

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The one answer is fine but requires a little reading into   Especially with the new terminology  stop    My Go -- organized by differences to make it useful in addition to the first answer by Daniel above   1  negative indexes   Substring requires positive indexes and will set a negative index to 0   Slice s negative index means the position from the end of the string    1234  substring -2  -1      1234  substring 0 0         1234  slice -2  -1      1234  slice 2  3      3    2  Swapping of indexes   Substring will reorder the indexes to make the first index less than or equal to the second index    1234  substring 3 2      1234  substring 2 3      3   1234  slice 3 2          --------------------------  General comment -- I find it weird that the second index is the position after the last character of the slice or substring   I would expect  1234  slice 2 2  to return  3    This makes Andy s confusion above justified -- I would expect  1234  slice 2  -1  to return  34    Yes  this means I m new to Javascript   This means also this behavior    1234  slice -2  -2          1234  slice -2  -1      3    1234  slice -2  -0         lt -- you have to use length or omit the argument to get the 4   1234  slice 3  -2          1234  slice 3  -1          1234  slice 3  -0         lt -- same issue  but seems weirder    My 2c

[javascript] What is the difference between String.slice and String.substring?

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