Repeat a string in JavaScript a number of times

Question

In Perl I can repeat a character multiple times using the syntax    a    a  x 10     results in  aaaaaaaaaa    Is there a simple way to accomplish this in Javascript  I can obviously use a function  but I was wondering if there was any built in approach  or some other clever technique

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I m going to expand on  bonbon s answer  His method is an easy way to  append N chars to an existing string   just in case anyone needs to do that  For example since  a google  is a 1 followed by 100 zeros    x000D   x000D  for var google    1   google length  lt  1   100  google     0     x000D  document getElementById  el   innerText   google  x000D   lt div gt This is  a google   lt  div gt  x000D   lt div id  el  gt  lt  div gt  x000D   x000D   x000D    NOTE  You do have to add the length of the original string to the conditional

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These days  the repeat string method is implemented almost everywhere   It is not in Internet Explorer   So unless you need to support older browsers  you can simply write    a  repeat 10    Before repeat  we used this hack   Array 11  join  a      create string with 10 a s   aaaaaaaaaa     Note that an array of length 11 gets you only 10  a s  since Array join puts the argument between the array elements    Simon also points out that according to this jsperf  it appears that it s faster in Safari and Chrome  but not Firefox  to repeat a character multiple times by simply appending using a for loop  although a bit less concise

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In a new ES6 harmony  you will have native way for doing this with repeat  Also ES6 right now only experimental  this feature is already available in Edge  FF  Chrome and Safari   abc  repeat 3      abcabcabc    And surely if repeat function is not available you can use old-good Array n   1  join  abc

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Right pads with zeros with no arrays or loops  Just uses repeat   using ES6 2015  which has wide support now  Left pads if you switch the concatenation  function pad text  maxLength      var res   text    quot 0 quot  repeat maxLength - text length     return res     console log pad  hello   8      hello000

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Here is what I use   function repeat str  num            var holder               for var i 0  i lt num  i                  holder push str                     return holder join

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this is how you can call a function and get the result by the helps of Array   and join     x000D   x000D  function repeatStringNumTimes str  num    x000D       repeat after me x000D    return num  gt  0   Array num 1  join str        x000D    x000D   x000D  console log repeatStringNumTimes  a  10   x000D   x000D   x000D

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Convenient if you repeat yourself a lot    x000D   x000D  String prototype repeat   String prototype repeat    function n   x000D    n  n    1  x000D    return Array n 1  join this   x000D    x000D   x000D  alert    Are we there yet  nNo  n  repeat 10     x000D   x000D   x000D

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In ES2015 ES6 you can use     repeat n    So just add this to your projects  and your are good to go     String prototype repeat   String prototype repeat         function n          if  n  lt  0  throw new RangeError  invalid count value          if  n    0  return           return new Array n   1  join this toString

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Can be used as a one-liner too   function repeat str  len        while  str length  lt  len  str    str substr 0  len-str length       return str

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Repeat a string  n -times  recursive      param  String  s - The string you want to repeat      param  Number  n - The times to repeat the string      param  String  d - A delimiter between each string       var repeat   function  s  n  d        return --n   s    d          repeat s  n  d         s      var foo    foo   console log        s n s n s n s        repeat foo              foo      repeat foo  2           foofoo      repeat foo   2          foofoo      repeat foo  2   -       foo-foo

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If you re not opposed to including a library in your project  lodash has a repeat function     repeat      3               https   lodash com docs repeat

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function repeatString n  string      var repeat         repeat length   n   1    return repeat join string      repeatString 3  x         gt  xxx repeatString 10           gt

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An alternative is    for var word       word length  lt  10  word     a       If you need to repeat multiple chars  multiply your conditional   for var word       word length  lt  10   3  word     foo       NOTE  You do not have to overshoot by 1 as with word   Array 11  join  a

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Array 10  fill  a   join       Although the most voted answer is a bit more compact  with this approach you don t have to add an extra array item

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In CoffeeScript      a  for dot in  0  10   join

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Lodash offers a similar functionality as the Javascript repeat   function which is not available in all browers  It is called   repeat and available since version 3 0 0     repeat  a   10

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Here is an ES6 version   x000D   x000D  const repeat    a n    gt  Array n  join a        split         x000D  repeat  A  20  forEach  a b    gt  console log a b 1   x000D   x000D   x000D

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For repeat a value in my projects i use repeat  For example   var n   6  for  i   0  i  lt  n  i          console log     repeat i 1       but be careful because this method has been added to the ECMAScript 6 specification

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var stringRepeat   function string  val      var newString           for var i   0  i  lt  val  i            newString push string         return newString join         var repeatedString   stringRepeat  a   1

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String prototype repeat   function  n    n   Math abs n     1  return Array n   1  join this                console log  0  repeat 3     0  repeat -3      return   000   000

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Another interesting way to quickly repeat n character is to use idea from quick exponentiation algorithm   var repeatString   function string  n        var result       i       for  i   1  i  lt   n  i    2            if   n  amp  i      i                result    string                    string   string   string             return result

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For all browsers  The following function will perform a lot faster than the option suggested in the accepted answer   var repeat   function str  count        var array           for var i   0  i  lt  count           array i      str      return array join          You d use it like this    var repeatedString   repeat  a   10     To compare the performance of this function with that of the option proposed in the accepted answer  see this Fiddle and this Fiddle for benchmarks   For moderns browsers only  In modern browsers  you can now do this using String prototype repeat method   var repeatedString    a  repeat 10     Read more about this method on MDN   This option is even faster  Unfortunately  it doesn t work in any version of Internet explorer  The numbers in the table specify the first browser version that fully supports the method

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The most performance-wice way is https   developer mozilla org en-US docs Web JavaScript Reference Global Objects String repeat  Short version is below     String prototype repeat   function count        if  count  lt  1  return         var result       pattern   this valueOf        while  count  gt  1          if  count  amp  1  result    pattern        count  gt  gt  gt   1  pattern    pattern            return result   pattern         var a    a     console debug a repeat 10      Polyfill from Mozilla   if   String prototype repeat      String prototype repeat   function count         use strict       if  this    null          throw new TypeError  can  t convert     this     to object              var str        this      count    count      if  count    count          count   0            if  count  lt  0          throw new RangeError  repeat count must be non-negative              if  count    Infinity          throw new RangeError  repeat count must be less than infinity              count   Math floor count       if  str length    0    count    0          return                  Ensuring count is a 31-bit integer allows us to heavily optimize the        main part  But anyway  most current  August 2014  browsers can t handle        strings 1  lt  lt  28 chars or longer  so      if  str length   count  gt   1  lt  lt  28          throw new RangeError  repeat count must not overflow maximum string size              var rpt           for              if   count  amp  1     1            rpt    str                count  gt  gt  gt   1        if  count    0            break                str    str               Could we try         return Array count   1  join this       return rpt

[javascript] Repeat a string in JavaScript a number of times

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