do something N times declarative syntax

Question

Is there a way in Javascript to write something like this easily    1 2 3  times do     something        Any library that might support some similar syntax maybe   Update  to clarify - I would like something   to be called 1 2 and 3 times respectively for each array element iteration

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calls doSomething 42 times Array  42   join   x    split       forEach  doSomething      and      creates 42 somethings var somethings   Array  42   join   x    split       map       gt  buildSomething         or   via https   stackoverflow com a 20066663 275501    Array apply null   length  42   forEach  doSomething

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TypeScript Implementation   For those of you who are interested in how to implement String times and Number times in a way that is type safe and works with the thisArg  here ya go   declare global       interface Number           times   callbackFn   iteration  number    gt  void  thisArg   any    gt  void            interface String           times   callbackFn   iteration  number    gt  void  thisArg   any    gt  void           Number prototype times   function  callbackFn  thisArg        const num   this valueOf       if  typeof callbackFn      function              throw new TypeError  callbackFn is not a function             if  num  lt  0            throw new RangeError  Must not be negative             if   isFinite num             throw new RangeError  Must be Finite             if  isNaN num             throw new RangeError  Must not be NaN                  Array num   forEach     i    gt  callbackFn bind thisArg  i   1            Other elegant solutions        new Array lt null gt  num  fill null  forEach      gt             Array from  length  num   forEach      gt         String prototype times   function  callbackFn  thisArg        let num   parseInt this valueOf        if  typeof callbackFn      function              throw new TypeError  callbackFn is not a function             if  num  lt  0            throw new RangeError  Must not be negative             if   isFinite num             throw new RangeError  Must be Finite                num is NaN if  this  is an empty string      if  isNaN num             num   0                Array num   forEach     i    gt  callbackFn bind thisArg  i   1            Other elegant solutions        new Array lt null gt  num  fill null  forEach      gt             Array from  length  num   forEach      gt          A link to the TypeScript Playground with some examples can be found here  This post implements solutions posted by  Andreas Bergstr  m  vinyll  Ozay Duman   amp  SeregPie

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This answer is based on Array forEach  without any library  just native vanilla   To basically call something   3 times  use    1 2 3  forEach function i      something          considering the following function   function something    console log  something       The outpout will be   something something something     To complete this questions  here s a way to do call something   1  2 and 3 times respectively   It s 2017  you may use ES6    1 2 3  forEach i   gt  Array i  fill i  forEach     gt      something         or in good old ES5    1 2 3  forEach function i      Array i  fill i  forEach function         something              In both cases  the outpout will be  The outpout will be   something  something something  something something something    once  then twice  then 3 times

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Using Array from and  forEach    x000D   x000D  let length   5  x000D  Array from  length   forEach  v  i    gt    x000D    console log     i     x000D      x000D   x000D   x000D

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These answers are all good and well and IMO  Andreas is the best  but many times in JS we have to do things asynchronously  in that case  async has you covered   http   caolan github io async docs html times  const async   require  async     async times 5  function n  next        createUser n  function err  user            next err  user              function err  users           we should now have 5 users       These  times  features arent very useful for most application code  but should be useful for testing

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Possible ES6 alternative   Array from Array 3   forEach  x  i    gt      something          And  if you want it  to be called 1 2 and 3 times respectively    Array from Array 3   forEach  x  i    gt      Array from Array i 1   forEach  x  i2    gt        console log  Something    i      i2                 Update   Taken from filling-arrays-with-undefined  This seems to be a more optimised way of creating the initial array  I ve also updated this to use the second parameter map function suggested by  felix-eve   Array from   length  3     x  i    gt      something

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var times    1 2 3    for var i   0  i  lt  times length   i        for var j   0  j  lt  times i  j              do something         Using jQuery  each       1 2 3   each function i  val      for var j   0  j  lt  val j              do something           OR  var x    1 2 3      x  each function i  val      for var j   0  j  lt  val j              do something           EDIT  You can do like below with pure JS   var times    1 2 3   times forEach function i          do something

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You can also do the same thing with destructuring as follows      Array 3   forEach      gt  console log  do something       or if you need index      Array 3   forEach      index    gt  console log  do something

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const loop  fn  times    gt      if   times    return     fn     loop fn  times - 1     loop something  3

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Create an Array and fill all items with undefined before using map     Array fill has no IE support  x000D   x000D     run 5 times  Array 5  fill   map  item  i   gt       console log i     print index    x000D   x000D   x000D   There is nice  quot trick quot  using destructuring Array  replacing fill with  Array 5  fill         Array 5   which does the same  filling the array with undefined   If you want to make the above more  quot declarative quot   my currently opinion-based solution would be   x000D   x000D  const iterate   times   gt  callback   gt      Array times   map  n i    gt  callback i    iterate 3  console log  x000D   x000D   x000D    Using old-school  reverse  loop   x000D   x000D     run 5 times  for  let i 5  i--       console log i   x000D   x000D   x000D   Or as a declarative  quot while quot    x000D   x000D  const times   count   gt  callback   gt    while count--  callback count     times 3  console log  x000D   x000D   x000D

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Array from  ES6  function doSomthing                Use it like so  Array from Array length  keys    forEach doSomthing    Or Array from   length     v  i    gt  i  forEach doSomthing    Or    array start counting from 1 Array from   length     v  i    gt    i  forEach doSomthing

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Assuming we can use some ES6 syntax like the spread operator  we ll want to do something as many times as the sum of all numbers in the collection   In this case if times is equal to  1 2 3   the total number of times will be 6  i e  1 2 3           param  number    times     param  cb  function     function doTimes times  cb         Get the sum of all the times   const totalTimes   times reduce  acc  time    gt  acc   time        Call the callback as many times as the sum       Array totalTimes   map cb      doTimes  1 2 3        gt  console log  something          gt  Prints  something  6 times   This post should be helpful if the logic behind constructing and spreading an array isn t apparent

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you can use  Array forEach  example   function logArrayElements element  index  array          console log  a     index            element          2  5  9  forEach logArrayElements    or with jQuery    each  52  97   function index  value       alert index          value          http   api jquery com jQuery each

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Just use a loop   var times   10  for var i 0  i  lt  times  i         doSomething

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With lodash     each  1  2  3    item    gt       doSomeThing item          Or    each  1  2  3   doSomeThing     Or if you want to do something N times   const N   10    times N       gt       doSomeThing           Or shorter    times N  doSomeThing     Refer to this link for lodash installation

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Given a function something   function something     console log  did something       And a new method times added to the Array prototype   Array prototype times   function f     for v of this       for var   of Array v         f        This code    1 2 3  times something    Outputs this   did something did something did something did something did something did something   Which I think answers your updated question  5 years later  but I wonder how useful it is to have this work on an array  Wouldn t the effect be the same as calling  6  times something   which in turn could be written as   for   of Array 6   something       although the use of   as a junk variable will probably clobber lodash or underscore if you re using it

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times   function          var length   arguments length      for  var i   0  i  lt  length   i              for  var j   0  j  lt  arguments i   j                  dosomthing                        You can call it like this   times 3 4   times 1 2 3 4   times 1 3 5 7 9

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There is a fantastic library called Ramda  which is similar to Underscore and Lodash  but is more powerful    const R   require  ramda     R call R times      gt        console log  do something       5     Ramda contains plenty of useful functions  See Ramda documentation

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If you can t use Underscorejs  you can implement it yourself  By attaching new methods to the Number and String prototypes  you could do it like this  using ES6 arrow functions       With String  5  times   i    gt  console log  number   i         With number variable var five   5  five times   i    gt  console log  number   i         With number literal  parentheses required   5  times   i    gt  console log  number   i       You simply have to create a function expression  of whatever name  and assign it to whatever property name  on the prototypes  you would like to access it as   var timesFunction   function callback      if  typeof callback      function          throw new TypeError  Callback is not a function        else if  isNaN parseInt Number this valueOf              throw new TypeError  Object is not a valid number          for  var i   0  i  lt  Number this valueOf     i          callback i           String prototype times   timesFunction  Number prototype times   timesFunction

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Since you mention Underscore   Assuming f is the function you want to call     each  1 2 3   function  n      times n  f        will do the trick  For example  with f   function  x    console log x      you will get on your console  0 0 1 0 1 2

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Just use a nested loop  maybe enclosed in a function   function times  fct  times       for  var i 0  i lt times length    i         for  var j 0  j lt times i     j           fct                  Then just call it like this   times  doSomething   1 2 3

[javascript] do <something> N times (declarative syntax)

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