Validate decimal numbers in JavaScript - IsNumeric

Question

What s the cleanest  most effective way to validate decimal numbers in JavaScript   Bonus points for    Clarity  Solution should be clean and simple  Cross-platform    Test cases   01  IsNumeric  -1          gt  true 02  IsNumeric  -1 5        gt  true 03  IsNumeric  0           gt  true 04  IsNumeric  0 42        gt  true 05  IsNumeric   42         gt  true 06  IsNumeric  99 999      gt  false 07  IsNumeric  0x89f       gt  false 08  IsNumeric   abcdef     gt  false 09  IsNumeric  1 2 3       gt  false 10  IsNumeric              gt  false 11  IsNumeric  blah        gt  false

User · Answer

I d like to add the following    1  IsNumeric  0x89f      true 2  IsNumeric  075      true   Positive hex numbers start with 0x and negative hex numbers start with -0x  Positive oct numbers start with 0 and negative oct numbers start with -0  This one takes most of what has already been mentioned into consideration  but includes hex and octal numbers  negative scientific  Infinity and has removed decimal scientific  4e3 2 is not valid    function IsNumeric input     var RE     -  0 INF  0 1-7  0-7     0x 0-9a-fA-F      0  1-9  0-9                    0-9      eE -  d           return  RE test input

User · Answer

Here I ve collected the  good ones  from this page and put them into a simple test pattern for you to evaluate on your own   For newbies  the console log is a built in function  available in all modern browsers  that lets you output results to the JavaScript console  dig around  you ll find it  rather than having to output to your HTML page   var isNumeric   function val          --------------------------        Recommended        --------------------------         jQuery - works rather well        See CMS s unit test also  http   dl getdropbox com u 35146 js tests isNumber html     return  isNaN parseFloat val    amp  amp  isFinite val           Aquatic - good and fast  fails the  0x89f  test  but that test is questionable        return parseFloat val   val          --------------------------        Other quirky options        --------------------------        Fails on     null  newline  tab negative        return  isNaN val           user532188 - fails on  0x89f        var n2   val        val   parseFloat val         return  val   NaN   amp  amp  n2  val           Rafael - fails on negative   decimal numbers  may be good for isInt           return   val   1    0     true   false          pottedmeat - good  but fails on stringy numbers  which may be a good thing for some folks        return   -  0  1-9  d             d      test val           Haren - passes all        borrowed from http   www codetoad com javascript isnumeric asp       var RE     - 0 1  d    0 1  d           return RE test val           YUI - good for strict adherance to number type  Doesn t let stringy numbers through        return typeof val      number   amp  amp  isFinite val           user189277 - fails on    and   n        return   val  gt  0    val  lt  0      var tests    0  1   0   0x0  0x000   0000    0x89f   8e5  0x23  -0  0 0   1 0   1 0  -1 5  0 42   075    01    -01    0      0    a    a2   true  false    000    1 2 3     abcdef             n     t    -   null  undefined    for  var i 0  i lt tests length  i         console log   test     i             tests i          t       isNumeric tests i

User · Answer

knockoutJs Inbuild library validation functions   By extending it the field get validated  1  number  self number   ko observable numberValue  extend   number  true     TestCase  numberValue    0 0     -- gt  true numberValue    0       -- gt  true numberValue    25      -- gt  true numberValue    -1      -- gt  true numberValue    -3 5    -- gt  true numberValue    11 112  -- gt  true numberValue    0x89f   -- gt  false numberValue            -- gt  false numberValue    sfsd    -- gt  false numberValue    dg      -- gt  false   2  digit  self number   ko observable numberValue  extend   digit  true     TestCase  numberValue    0       -- gt  true numberValue    25      -- gt  true numberValue    0 0     -- gt  false numberValue    -1      -- gt  false numberValue    -3 5    -- gt  false numberValue    11 112  -- gt  false numberValue    0x89f   -- gt  false numberValue            -- gt  false numberValue    sfsd    -- gt  false numberValue    dg      -- gt  false   3  min and max  self number   ko observable numberValue  extend   min  5   extend   max  10     This field accept value between 5 and 10 only  TestCase  numberValue    5     -- gt  true numberValue    6     -- gt  true numberValue    6 5   -- gt  true numberValue    9     -- gt  true numberValue    11    -- gt  false numberValue    0     -- gt  false numberValue         -- gt  false

User · Answer

function IsNumeric num         return  num  gt  0    num  lt  0       This works for 0x23 type numbers as well

User · Answer

I think my code is perfect       x000D   x000D      x000D      param  string  s x000D      return  boolean  x000D      x000D  var isNumber   function s    x000D      return s trim         amp  amp   isNaN Number s    x000D     x000D   x000D   x000D

User · Answer

I have run the following below and it passes all the test cases     It makes use of the different way in which parseFloat and Number handle their inputs     function IsNumeric  in        return  parseFloat  in      Number  in   amp  amp  Number  in      NaN

User · Answer

This way seems to work well   function IsNumeric input       var RE     - 0 1  d    0 1  d         return  RE test input        In one line   const IsNumeric    num    gt    - 0 1  d    0 1  d    test num     And to test it    x000D   x000D  const IsNumeric    num    gt    - 0 1  d    0 1  d    test num   x000D       x000D      function TestIsNumeric    x000D          var results      x000D          results     IsNumeric  -1    Pass   Fail        IsNumeric  -1     gt  true n   x000D          results     IsNumeric  -1 5    Pass   Fail        IsNumeric  -1 5     gt  true n   x000D          results     IsNumeric  0    Pass   Fail        IsNumeric  0     gt  true n   x000D          results     IsNumeric  0 42    Pass   Fail        IsNumeric  0 42     gt  true n   x000D          results     IsNumeric   42    Pass   Fail        IsNumeric   42     gt  true n   x000D          results      IsNumeric  99 999    Pass   Fail        IsNumeric  99 999     gt  false n   x000D          results      IsNumeric  0x89f    Pass   Fail        IsNumeric  0x89f     gt  false n   x000D          results      IsNumeric   abcdef    Pass   Fail        IsNumeric   abcdef     gt  false n   x000D          results      IsNumeric  1 2 3    Pass   Fail        IsNumeric  1 2 3     gt  false n   x000D          results      IsNumeric      Pass   Fail        IsNumeric       gt  false n   x000D          results      IsNumeric  blah    Pass   Fail        IsNumeric  blah     gt  false n   x000D           x000D          return results  x000D        x000D   x000D  console log TestIsNumeric     x000D   as-console-wrapper   max-height  100   important  top  0    x000D   x000D   x000D    I borrowed that regex from http   www codetoad com javascript isnumeric asp  Explanation      match beginning of string - 0 1  optional negative sign  d  optional digits    0 1  optional decimal point  d  at least one digit    match end of string

User · Answer

One can use a type-check library like https   github com arasatasaygin is js or just extract a check snippet from there  https   github com arasatasaygin is js blob master is js L131    is nan   function value          NaN is number       return value     value         is a given value number  is number   function value        return  is nan value   amp  amp  Object prototype toString call value        object Number         In general if  you need it to validate parameter types  on entry point of function call   you can go with JSDOC-compliant contracts  https   www npmjs com package bycontract           This is JSDOC syntax     param  number string  sum     param  Object  lt string  string gt   payload     param  function  cb     function foo  sum  payload  cb          Test if the contract is respected at entry point   byContract  arguments     number string    Object  lt string  string gt     function            Test it foo  100    foo   foo     function          ok foo  100    foo  100    function          exception

User · Answer

None of the answers return false for empty strings  a fix for that     function is numeric n     return  n        amp  amp   isNaN parseFloat n    amp  amp  isFinite n

User · Answer

I found simple solution  probably not best but it s working fine     So  what I do is next  I parse string to Int and check if length size of new variable which is now int type is same as length of original string variable  Logically if size is the same it means string is fully parsed to int and that is only possible if string is  made  only of numbers   var val 1   e  val       var n parseInt val      if val length    n length  alert  Is int      You can easily put that code in function and instead of alert use return true if int  Remember  if you use dot or comma in string you are checking it s still false cos you are parsing to int   Note  Adding 1  on e val so starting zero wouldn t be removed

User · Answer

Yahoo  UI uses this   isNumber  function o        return typeof o      number   amp  amp  isFinite o

User · Answer

CMS  answer  Your snippet failed on whitespace cases on my machine using nodejs  So I combined it with   joel s answer to the following   is float   function v        return  isNaN v   amp  amp  isFinite v   amp  amp           typeof v      number     v replace    s   s   g      length  gt  0       I unittested it with those cases that are floats   var t             0          1 2123           0            2123 4           -1           -1           -123 423           -123 432           07          0xad           07            0xad           and those cases that are no floats  including empty whitespaces and objects   arrays        var t              hallo                                    jklsd0                         t             n                        Everything works as expected here  Maybe this helps   Full source code for this can be found here

User · Answer

return  input - 0     input  amp  amp  input length  gt  0    didn t work for me  When I put in an alert and tested  input length was undefined  I think there is no property to check integer length  So what I did was  var temp        input  return  input - 0     input  amp  amp  temp length  gt  0    It worked fine

User · Answer

Use the function isNaN  I believe if you test for  isNaN yourstringhere  it works fine for any of these situations

User · Answer

If I m not mistaken  this should match any valid JavaScript number value  excluding constants  Infinity  NaN  and the sign operators   -  because they are not actually part of the number as far as I concerned  they are separate operators    I needed this for a tokenizer  where sending the number to JavaScript for evaluation wasn t an option    It s definitely not the shortest possible regular expression  but I believe it catches all the finer subtleties of JavaScript s number syntax               1-9  d   d    d      1-9  d   d     d      1-9  d   d        e  d    0 0-7   0x 0-9a-f     i   Valid numbers would include    - 0  - 00  - 01  - 10  - 0e1  - 0e01  -  0  - 0   -  0e1  - 0 e1  - 0 e00  - 0xf  - 0Xf   Invalid numbers would be   - 00e1  - 01e1  - 00 0  - 00x0  -    -  e0

User · Answer

Yeah  the built-in isNaN object  will be much faster than any regex parsing  because it s built-in and compiled  instead of interpreted on the fly   Although the results are somewhat different to what you re looking for  try it                                                     IS NUMERIC document write  isNaN  -1       lt br   gt             true document write  isNaN  -1 5       lt br   gt           true document write  isNaN  0       lt br   gt              true document write  isNaN  0 42       lt br   gt           true document write  isNaN   42       lt br   gt            true document write  isNaN  99 999       lt br   gt         false document write  isNaN  0x89f       lt br   gt          true document write  isNaN   abcdef       lt br   gt        false document write  isNaN  1 2 3       lt br   gt          false document write  isNaN         lt br   gt               true document write  isNaN  blah       lt br   gt           false

User · Answer

To me  this is the best way   isNumber   function v      return typeof v      number   amp  amp  isFinite v

User · Answer

The accepted answer failed your test  7 and I guess it s because you changed your mind  So this is a response to the accepted answer  with which I had issues   During some projects I have needed to validate some data and be as certain as possible that it is a javascript numerical value that can be used in mathematical operations   jQuery  and some other javascript libraries already include such a function  usually called isNumeric  There is also a post on stackoverflow that has been widely accepted as the answer  the same general routine that the afore mentioned libraries are using   function isNumber n      return  isNaN parseFloat n    amp  amp  isFinite n       First  the code above would return true if the argument was an array of length 1  and that single element was of a type deemed as numeric by the above logic  In my opinion  if it s an array then its not numeric   To alleviate this problem  I added a check to discount arrays from the logic  function isNumber n      return Object prototype toString call n        object Array    amp  amp  isNaN parseFloat n    amp  amp  isFinite n       Of course  you could also use Array isArray  jquery   isArray or prototype Object isArray instead of Object prototype toString call n        object Array    My second issue was that Negative Hexadecimal integer literal strings   -0xA  -  -10  were not being counted as numeric  However  Positive Hexadecimal integer literal strings   0xA  -  10  were treated as numeric  I needed both to be valid numeric   I then modified the logic to take this into account   function isNumber n      return Object prototype toString call n        object Array    amp  amp  isNaN parseFloat n    amp  amp  isFinite n toString   replace   -             If you are worried about the creation of the regex each time the function is called then you could rewrite it within a closure  something like this  var isNumber    function        var rx     -      return function  n          return Object prototype toString call n        object Array    amp  amp  isNaN parseFloat n    amp  amp  isFinite n toString   replace rx                     I then took CMSs  30 test cases and cloned the testing on jsfiddle added my extra test cases and my above described solution   It may not replace the widely accepted used answer but if this is more of what you are expecting as results from your isNumeric function then hopefully this will be of some help   EDIT  As pointed out by Bergi  there are other possible objects that could be considered numeric and it would be better to whitelist than blacklist  With this in mind I would add to the criteria   I want my isNumeric function to consider only Numbers or Strings  With this in mind  it would be better to use  function isNumber n      return  Object prototype toString call n        object Number      Object prototype toString call n        object String     amp  amp  isNaN parseFloat n    amp  amp  isFinite n toString   replace   -             Test the solutions   x000D   x000D  var testHelper   function     x000D   x000D    var testSuite   function     x000D      test  Integer Literals   function     x000D        ok isNumber  -10     Negative integer string    x000D        ok isNumber  0     Zero string    x000D        ok isNumber  5     Positive integer string    x000D        ok isNumber -16    Negative integer number    x000D        ok isNumber 0    Zero integer number    x000D        ok isNumber 32    Positive integer number    x000D        ok isNumber  040     Octal integer literal string    x000D        ok isNumber 0144    Octal integer literal    x000D        ok isNumber  -040     Negative Octal integer literal string    x000D        ok isNumber -0144    Negative Octal integer literal    x000D        ok isNumber  0xFF     Hexadecimal integer literal string    x000D        ok isNumber 0xFFF    Hexadecimal integer literal    x000D        ok isNumber  -0xFF     Negative Hexadecimal integer literal string    x000D        ok isNumber -0xFFF    Negative Hexadecimal integer literal    x000D          x000D   x000D      test  Foating-Point Literals   function     x000D        ok isNumber  -1 6     Negative floating point string    x000D        ok isNumber  4 536     Positive floating point string    x000D        ok isNumber -2 6    Negative floating point number    x000D        ok isNumber 3 1415    Positive floating point number    x000D        ok isNumber 8e5    Exponential notation    x000D        ok isNumber  123e-2     Exponential notation string    x000D          x000D   x000D      test  Non-Numeric values   function     x000D        equals isNumber      false   Empty string    x000D        equals isNumber              false   Whitespace characters string    x000D        equals isNumber   t t    false   Tab characters string    x000D        equals isNumber  abcdefghijklm1234567890    false   Alphanumeric character string    x000D        equals isNumber  xabcdefx    false   Non-numeric character string    x000D        equals isNumber true   false   Boolean true literal    x000D        equals isNumber false   false   Boolean false literal    x000D        equals isNumber  bcfed5 2    false   Number with preceding non-numeric characters    x000D        equals isNumber  7 2acdgs    false   Number with trailling non-numeric characters    x000D        equals isNumber undefined   false   Undefined value    x000D        equals isNumber null   false   Null value    x000D        equals isNumber NaN   false   NaN value    x000D        equals isNumber Infinity   false   Infinity primitive    x000D        equals isNumber Number POSITIVE INFINITY   false   Positive Infinity    x000D        equals isNumber Number NEGATIVE INFINITY   false   Negative Infinity    x000D        equals isNumber new Date 2009  1  1    false   Date object    x000D        equals isNumber new Object     false   Empty object    x000D        equals isNumber function        false   Instance of a function    x000D        equals isNumber      false   Empty Array    x000D        equals isNumber   -10     false   Array Negative integer string    x000D        equals isNumber   0     false   Array Zero string    x000D        equals isNumber   5     false   Array Positive integer string    x000D        equals isNumber  -16    false   Array Negative integer number    x000D        equals isNumber  0    false   Array Zero integer number    x000D        equals isNumber  32    false   Array Positive integer number    x000D        equals isNumber   040     false   Array Octal integer literal string    x000D        equals isNumber  0144    false   Array Octal integer literal    x000D        equals isNumber   -040     false   Array Negative Octal integer literal string    x000D        equals isNumber  -0144    false   Array Negative Octal integer literal    x000D        equals isNumber   0xFF     false   Array Hexadecimal integer literal string    x000D        equals isNumber  0xFFF    false   Array Hexadecimal integer literal    x000D        equals isNumber   -0xFF     false   Array Negative Hexadecimal integer literal string    x000D        equals isNumber  -0xFFF    false   Array Negative Hexadecimal integer literal    x000D        equals isNumber  1  2    false   Array with more than 1 Positive interger number    x000D        equals isNumber  -1  -2    false   Array with more than 1 Negative interger number    x000D          x000D      x000D   x000D    var functionsToTest     x000D   x000D      function n    x000D        return  isNaN parseFloat n    amp  amp  isFinite n   x000D         x000D   x000D      function n    x000D        return  isNaN n   amp  amp   isNaN parseFloat n    x000D         x000D   x000D      function n    x000D        return  isNaN  n    x000D         x000D   x000D      function n    x000D        return  isNaN parseFloat n    x000D         x000D   x000D      function n    x000D        return typeof n      boolean   amp  amp   isNaN n   x000D         x000D   x000D      function n    x000D        return parseFloat n      Number n   x000D         x000D   x000D      function n    x000D        return parseInt n      Number n   x000D         x000D   x000D      function n    x000D        return  isNaN Number String n     x000D         x000D   x000D      function n    x000D        return  isNaN        n    x000D         x000D   x000D      function n    x000D        return   n     n  x000D         x000D   x000D      function n    x000D        return n  amp  amp    -  d     d      test n        x000D         x000D   x000D      function n    x000D        return isFinite Number String n     x000D         x000D   x000D      function n    x000D        return isFinite String n    x000D         x000D   x000D      function n    x000D        return  isNaN n   amp  amp   isNaN parseFloat n    amp  amp  isFinite n   x000D         x000D   x000D      function n    x000D        return parseFloat n     n  x000D         x000D   x000D      function n    x000D        return  n - 0     n  amp  amp  n length  gt  0  x000D         x000D   x000D      function n    x000D        return typeof n      number   amp  amp  isFinite n   x000D         x000D   x000D      function n    x000D        return  Array isArray n   amp  amp   isNaN parseFloat n    amp  amp  isFinite n toString   replace   -         x000D        x000D   x000D       x000D   x000D   x000D       Examines the functionsToTest array  extracts the return statement of each function x000D       and fills the toTest select element  x000D    var fillToTestSelect   function     x000D      for  var i   0  i  lt  functionsToTest length  i      x000D        var f   functionsToTest i  toString    x000D        var option      s S  return    s S      exec f  1   x000D            toTest   append   lt option value      i      gt      i   1           option     lt  option gt     x000D        x000D      x000D   x000D    var performTest   function functionNumber    x000D      reset       Reset previous test x000D          tests   html        Clean test results x000D      isNumber   functionsToTest functionNumber      Override the isNumber global function with the one to test x000D      testSuite       Run the test x000D   x000D         Get test results x000D      var totalFail   0  x000D      var totalPass   0  x000D         b fail   each function     x000D        totalFail    Number   this  html     x000D          x000D         b pass   each function     x000D        totalPass    Number   this  html     x000D          x000D          testresult   html totalFail     of      totalFail   totalPass      test failed     x000D   x000D          banner   attr  class       addClass totalFail  gt  0    fail     pass    x000D      x000D   x000D    return   x000D      performTest  performTest  x000D      fillToTestSelect  fillToTestSelect  x000D      testSuite  testSuite x000D       x000D       x000D   x000D   x000D    document  ready function     x000D    testHelper fillToTestSelect    x000D    testHelper performTest 0   x000D   x000D        toTest   change function     x000D      testHelper performTest   this  children   selected   val     x000D        x000D      x000D   lt script src  https   ajax googleapis com ajax libs jquery 1 11 1 jquery min js  type  text javascript  gt  lt  script gt  x000D   lt script src  https   rawgit com Xotic750 testrunner-old master testrunner js  type  text javascript  gt  lt  script gt  x000D   lt link href  https   rawgit com Xotic750 testrunner-old master testrunner css  rel  stylesheet  type  text css  gt  x000D   lt h1 gt isNumber Test Cases lt  h1 gt  x000D   x000D   lt h2 id  banner  class  pass  gt  lt  h2 gt  x000D   x000D   lt h2 id  userAgent  gt Mozilla 5 0  X11  Linux x86 64  AppleWebKit 537 11  KHTML  like Gecko  Chrome 23 0 1271 95 Safari 537 11 lt  h2 gt  x000D   x000D   lt div id  currentFunction  gt  lt  div gt  x000D   x000D   lt div id  selectFunction  gt  x000D     lt label for  toTest  style  font-weight bold  font-size Large   gt Select function to test  lt  label gt  x000D     lt select id  toTest  name  toTest  gt  x000D     lt  select gt  x000D   lt  div gt  x000D   x000D   lt div id  testCode  gt  lt  div gt  x000D   x000D   lt ol id  tests  gt  x000D     lt li class  pass  gt  x000D       lt strong gt Integer Literals  lt b style  color black   gt  0  10  10  lt  b gt  lt  strong gt  x000D   x000D       lt ol style  display  none   gt  x000D         lt li class  pass  gt Negative integer string lt  li gt  x000D   x000D         lt li class  pass  gt Zero string lt  li gt  x000D   x000D         lt li class  pass  gt Positive integer string lt  li gt  x000D   x000D         lt li class  pass  gt Negative integer number lt  li gt  x000D   x000D         lt li class  pass  gt Zero integer number lt  li gt  x000D   x000D         lt li class  pass  gt Positive integer number lt  li gt  x000D   x000D         lt li class  pass  gt Octal integer literal string lt  li gt  x000D   x000D         lt li class  pass  gt Octal integer literal lt  li gt  x000D   x000D         lt li class  pass  gt Hexadecimal integer literal string lt  li gt  x000D   x000D         lt li class  pass  gt Hexadecimal integer literal lt  li gt  x000D       lt  ol gt  x000D     lt  li gt  x000D   x000D     lt li class  pass  gt  x000D       lt strong gt Foating-Point Literals  lt b style  color black   gt  0  6  6  lt  b gt  lt  strong gt  x000D   x000D       lt ol style  display  none   gt  x000D         lt li class  pass  gt Negative floating point string lt  li gt  x000D   x000D         lt li class  pass  gt Positive floating point string lt  li gt  x000D   x000D         lt li class  pass  gt Negative floating point number lt  li gt  x000D   x000D         lt li class  pass  gt Positive floating point number lt  li gt  x000D   x000D         lt li class  pass  gt Exponential notation lt  li gt  x000D   x000D         lt li class  pass  gt Exponential notation string lt  li gt  x000D       lt  ol gt  x000D     lt  li gt  x000D   x000D     lt li class  pass  gt  x000D       lt strong gt Non-Numeric values  lt b style  color black   gt  0  18  18  lt  b gt  lt  strong gt  x000D   x000D       lt ol style  display  none   gt  x000D         lt li class  pass  gt Empty string  false lt  li gt  x000D   x000D         lt li class  pass  gt Whitespace characters string  false lt  li gt  x000D   x000D         lt li class  pass  gt Tab characters string  false lt  li gt  x000D   x000D         lt li class  pass  gt Alphanumeric character string  false lt  li gt  x000D   x000D         lt li class  pass  gt Non-numeric character string  false lt  li gt  x000D   x000D         lt li class  pass  gt Boolean true literal  false lt  li gt  x000D   x000D         lt li class  pass  gt Boolean false literal  false lt  li gt  x000D   x000D         lt li class  pass  gt Number with preceding non-numeric characters  false lt  li gt  x000D   x000D         lt li class  pass  gt Number with trailling non-numeric characters  false lt  li gt  x000D   x000D         lt li class  pass  gt Undefined value  false lt  li gt  x000D   x000D         lt li class  pass  gt Null value  false lt  li gt  x000D   x000D         lt li class  pass  gt NaN value  false lt  li gt  x000D   x000D         lt li class  pass  gt Infinity primitive  false lt  li gt  x000D   x000D         lt li class  pass  gt Positive Infinity  false lt  li gt  x000D   x000D         lt li class  pass  gt Negative Infinity  false lt  li gt  x000D   x000D         lt li class  pass  gt Date object  false lt  li gt  x000D   x000D         lt li class  pass  gt Empty object  false lt  li gt  x000D   x000D         lt li class  pass  gt Instance of a function  false lt  li gt  x000D       lt  ol gt  x000D     lt  li gt  x000D   lt  ol gt  x000D   x000D   lt div id  main  gt  x000D    This page contains tests for a set of isNumber functions  To see them  take a look at the source  x000D   lt  div gt  x000D   x000D   lt div gt  x000D     lt p class  result  gt Tests completed in 0 milliseconds  x000D       lt br gt 0 tests of 0 failed  lt  p gt  x000D   lt  div gt  x000D   x000D   x000D

User · Answer

function isNumeric n        var isNumber   true         each n replace    g     toString    function i  v           if v       amp  amp  v       amp  amp  v   -                if isNaN v                   isNumber   false                 return false                                         return isNumber     isNumeric -3 4567 89        true  lt br gt   isNumeric 3 4567 89        true  lt br gt   isNumeric  -3 4567 89         true  lt br gt   isNumeric 3d 4567 89        false

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rsval   bind  keypress   function e             var asciiCodeOfNumbers    48 46  49  50  51  52  53  54  54  55  56  57           var keynum     window event    e which   e keyCode           var splitn   this value split                var decimal   splitn length          var precision   splitn 1            if decimal    2  amp  amp  precision length  gt   2      console log precision    e      e preventDefault               if  keynum    46                  if decimal  gt  2    e preventDefault                           if    inArray keynum  asciiCodeOfNumbers     -1              e preventDefault

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function isNumber n        return  n   n     n   n-0   amp  amp  n 0  0  amp  amp    S  test n       Explanations    n   n-0  n   n     verifies if n is a number or a string  discards arrays  boolean  date  null        You can replace  n   n-0  n   n     by n   undefined  amp  amp  n   null  amp  amp   n constructor   Number  n constructor   String   significantly faster but less concise   n 0  0 verifies if n is a finite number as isFinite n  does  If you need to check strings that represent negative hexadecimal  just replace n 0  0 by something like n toString   replace    s -      0  0  It costs a little of course  so if you don t need it  don t use it     S  test n  discards empty strings or strings  that contain only white-spaces  necessary since isFinite n  or n 0  0 return a false positive in this case   You can reduce the number of call to  test n  by using  n  0   0  test n   instead of   S  test n   or you can use a slightly faster but less concise test such as  n  0   n     indexOf  0   gt  0   tiny improvement

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Since jQuery 1 7  you can use jQuery isNumeric       isNumeric  -1            true   isNumeric  -1 5          true   isNumeric  0             true   isNumeric  0 42          true   isNumeric   42           true   isNumeric  0x89f         true  valid hexa number    isNumeric  99 999        false   isNumeric   abcdef       false   isNumeric  1 2 3         false   isNumeric                false   isNumeric  blah          false   Just note that unlike what you said  0x89f is a valid number  hexa

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It can be done without RegExp as   function IsNumeric data       return parseFloat data   data

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No need to use extra lib   const IsNumeric       numbers    gt      return numbers reduce  pre  cur    gt  pre  amp  amp     cur     0     cur   true        Test   gt  IsNumeric 1  true  gt  IsNumeric 1 2 3  true  gt  IsNumeric 1 2 3 0  true  gt  IsNumeric 1 2 3 0     false  gt  IsNumeric 1 2 3 0  2   true  gt  IsNumeric 1 2 3 0  200   true  gt  IsNumeric 1 2 3 0  -200   true  gt  IsNumeric 1 2 3 0  -200    32   true

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isNumeric  el   gt  return Boolean parseFloat el    amp  amp  isFinite el    Nothing very different but we can use Boolean constructor

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I use this way to chack that varible is numeric   v   1    v

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Zoltan Lengyel  other locales  comment  Apr 26 at 2 14  in  CMS Dec answer  2  09 at 5 36    I would recommend testing for typeof  n       string        function isNumber n            if  typeof  n       string                 n   n replace                              return  isNaN parseFloat n    amp  amp  isFinite n           This extends Zoltans recommendation to not only be able to test  localized numbers  like  isNumber  12 50   but also  pure  numbers like isNumber 2011

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A simple and clean solution by leveraging language s dynamic type checking   function IsNumeric  string       if string         repeat string length         return false         return string - 0     string   1      if you don t care about white-spaces you can remove that   if     see test cases below   x000D   x000D  function IsNumeric  string    x000D     if string         repeat string length    x000D        return false x000D       x000D     return string - 0     string   1 x000D    x000D   x000D   x000D  console log  -1            IsNumeric  -1        x000D  console log  -1 5            IsNumeric  -1 5     x000D  console log  0            IsNumeric  0         x000D  console log  0 42            IsNumeric  0 42       x000D  console log   42            IsNumeric   42        x000D  console log  99 999            IsNumeric  99 999    x000D  console log  0x89f            IsNumeric  0x89f      x000D  console log   abcdef            IsNumeric   abcdef    x000D  console log  1 2 3            IsNumeric  1 2 3     x000D  console log              IsNumeric          x000D  console log  33             IsNumeric  33     x000D   x000D   x000D

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function inNumeric n      return Number n  toString       n      If n is numeric Number n  will return the numeric value and toString   will turn it back to a string  But if n isn t numeric Number n  will return NaN so it won t match the original n

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Only problem I had with  CMS s answer is the exclusion of NaN and Infinity  which are useful numbers for many situations  One way to check for NaN s is to check for numeric values that don t equal themselves  NaN    NaN   So there are really 3 tests you d like to deal with      function isNumber n      n   parseFloat n     return  isNaN n     n    n    function isFiniteNumber n      n   parseFloat n     return  isNaN n   amp  amp  isFinite n         function isComparableNumber n      n   parseFloat n     return  n  gt  0    n  lt  0      isFiniteNumber  NaN   false isFiniteNumber  OxFF   true isNumber  NaN   true isNumber 1 0-1 0  true isComparableNumber  NaN   false isComparableNumber  Infinity   true   My isComparableNumber is pretty close to another elegant answer  but handles hex and other string representations of numbers

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I realize the original question did not mention jQuery  but if you do use jQuery  you can do     isNumeric val    Simple   https   api jquery com jQuery isNumeric   as of jQuery 1 7

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This should work  Some of the functions provided here are flawed  also should be faster than any other function here           function isNumeric n                        var n2   n              n   parseFloat n               return  n   NaN   amp  amp  n2  n               Explained   Create a copy of itself  then converts the number into float  then compares itself with the original number  if it is still a number   whether integer or float    and matches the original number  that means  it is indeed a number   It works with numeric strings as well as plain numbers  Does not work with hexadecimal numbers    Warning  use at your own risk  no guarantees

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To check if a variable contains a valid number and not just a String which looks like a number  Number isFinite value  can be used   This is part of the language since ES2015  Examples   Number isFinite Infinity       false Number isFinite NaN            false Number isFinite -Infinity      false  Number isFinite 0              true Number isFinite 2e64           true  Number isFinite  0             false Number isFinite null           false

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A couple of tests to add   IsNumeric  01 05     gt  false IsNumeric  1      gt  false IsNumeric        gt  false   I came up with this   function IsNumeric input        return   -  0  1-9  d             d      test input       The solution covers    An optional negative sign at the beginning A single zero  or one or more digits not starting with 0  or nothing so long as a period follows A period that is followed by 1 or more numbers

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The following seems to works fine for many cases   function isNumeric num        return  num  gt  0    num     0    num      0     num  lt  0   amp  amp  num     true  amp  amp  isFinite num       This is built on top of this answer  which is for this answer too   https   stackoverflow com a 1561597 1985601

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Best way to do this is like this   function isThisActuallyANumber data       return   typeof data      number   amp  amp   isNaN data

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I m using simpler solution   function isNumber num        return parseFloat num  toString      num

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Arrrgh   Don t listen to the regular expression answers   RegEx is icky for this  and I m not talking just performance   It s so easy to make subtle  impossible to spot mistakes with your regular expression     If you can t use isNaN    this should work much better   function IsNumeric input        return  input - 0     input  amp  amp      input  trim   length  gt  0      Here s how it works   The  input - 0  expression forces JavaScript to do type coercion on your input value  it must first be interpreted as a number for the subtraction operation   If that conversion to a number fails  the expression will result in NaN   This numeric result is then compared to the original value you passed in   Since the left hand side is now numeric  type coercion is again used   Now that the input from both sides was coerced to the same type from the same original value  you would think they should always be the same  always true   However  there s a special rule that says NaN is never equal to NaN  and so a value that can t be converted to a number  and only values that cannot be converted to numbers  will result in false    The check on the length is for a special case involving empty strings  Also note that it falls down on your 0x89f test  but that s because in many environments that s an okay way to define a number literal   If you want to catch that specific scenario you could add an additional check   Even better  if that s your reason for not using isNaN   then just wrap your own function around isNaN   that can also do the additional check   In summary  if you want to know if a value can be converted to a number  actually try to convert it to a number     I went back and did some research for why a whitespace string did not have the expected output  and I think I get it now  an empty string is coerced to 0 rather than NaN  Simply trimming the string before the length check will handle this case   Running the unit tests against the new code and it only fails on the infinity and boolean literals  and the only time that should be a problem is if you re generating code  really  who would type in a literal and check if it s numeric  You should know   and that would be some strange code to generate   But  again  the only reason ever to use this is if for some reason you have to avoid isNaN

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I realize this has been answered many times  but the following is a decent candidate which can be useful in some scenarios   it should be noted that it assumes that   42  is NOT a number  and  4   is NOT a number  so this should be taken into account   function isDecimal x      return      x           x     function isInteger x      return      x          parseInt x       The isDecimal passes the following test   function testIsNumber f      return f  -1    amp  amp  f  -1 5    amp  amp  f  0    amp  amp  f  0 42        amp  amp   f   42    amp  amp   f  99 999    amp  amp   f  0x89f        amp  amp   f   abcdef    amp  amp   f  1 2 3    amp  amp   f      amp  amp   f  blah        The idea here is that every number or integer has one  canonical  string representation  and every non-canonical representation should be rejected  So we cast to a number and back  and see if the result is the original string   Whether these functions are useful for you depends on the use case  One feature is that distinct strings represent distinct numbers  if both pass the isNumber   test    This is relevant e g  for numbers as object property names   var obj       obj  4      canonical 4   obj  04      alias of 4   obj 4       prints  canonical 4  to the console

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You can minimize this function in a lot of way  and you can also implement it with a custom regex for negative values or custom charts       number   on  input  function        var n   this  val   replace    g     replace   D g          if     isNumeric n             this  val n slice 0  -1       else           this  val n

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An integer value can be verified by   function isNumeric value        var bool   isNaN  value        bool   bool     value indexOf         -1       bool   bool     value indexOf         -1       return  bool       This way is easier and faster  All tests are checked

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Here s a lil bit improved version  probably the fastest way out there  that I use instead of exact jQuery s variant  I really don t know why don t they use this one   function isNumeric val        return  isNaN  val   amp  amp  isFinite val       The downside of jQuery s version is that if you pass a string with leading numerics and trailing letters like  123abc  the parseFloat   parseInt will extract the numeric fraction out and return 123  BUT  the second guard isFinite will fail it anyway  With the unary   operator it will die on the very first guard since   throws NaN for such hybrids    A little performance yet I think a solid semantic gain

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My solution   function isNumeric input        var number      - 0 1     0-9    0 1       0-9    0 1   i      var regex   RegExp number       return regex test input   amp  amp  input length gt 0      It appears to work in every situation  but I might be wrong

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I think parseFloat function can do all the work here  The function below passes all the tests on this page including isNumeric Infinity     true   function isNumeric n         return parseFloat n     n

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Here s a dead-simple one  tested in Chrome  Firefox  and IE    function isNumeric x      return parseFloat x     x      Test cases from question   console log  trues    console log isNumeric  -1     console log isNumeric  -1 5     console log isNumeric  0     console log isNumeric  0 42     console log isNumeric   42      console log  falses    console log isNumeric  99 999     console log isNumeric  0x89f     console log isNumeric   abcdef     console log isNumeric  1 2 3     console log isNumeric       console log isNumeric  blah       Some more test cases   console log  trues    console log isNumeric 0    console log isNumeric -1    console log isNumeric -500    console log isNumeric 15000    console log isNumeric 0 35    console log isNumeric -10 35    console log isNumeric 2 534e25    console log isNumeric  2 534e25     console log isNumeric  52334     console log isNumeric  -234     console log isNumeric Infinity    console log isNumeric -Infinity    console log isNumeric  Infinity     console log isNumeric  -Infinity      console log  falses    console log isNumeric NaN    console log isNumeric       console log isNumeric       console log isNumeric       console log isNumeric  one     console log isNumeric true    console log isNumeric false    console log isNumeric     console log isNumeric undefined    console log isNumeric null    console log isNumeric  -234aa       Note that it considers infinity a number

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If you need to validate a special set of decimals y you can use this simple javascript   http   codesheet org codesheet x1kI7hAD   lt input type  text  name  date  value    pattern   0-9   1 2      1   0-9   2   maxlength  6  placeholder  od npr   16 06  onchange  date this      gt    The Javascript   function date inputField              var isValid       0-9   1 2      1   0-9   2    test inputField value        if  isValid        inputField style backgroundColor     bfa       else       inputField style backgroundColor     fba         return isValid

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Joel s answer is pretty close  but it will fail in the following cases      Whitespace strings  IsNumeric            true  IsNumeric   t t      true  IsNumeric   n r      true      Number literals  IsNumeric -1      false  IsNumeric 0       false  IsNumeric 1 1     false  IsNumeric 8e5     false    Some time ago I had to implement an IsNumeric function  to find out if a variable contained a numeric value  regardless of its type  it could be a String containing a numeric value  I had to consider also exponential notation  etc    a Number object  virtually anything could be passed to that function  I couldn t make any type assumptions   taking care of type coercion  eg   true    1  but true shouldn t be considered as  numeric     I think is worth sharing this set of  30 unit tests made to numerous function implementations  and also share the one that passes all my tests   function isNumeric n        return  isNaN parseFloat n    amp  amp  isFinite n       P S  isNaN  amp  isFinite have a confusing behavior due to forced conversion to number  In ES6  Number isNaN  amp  Number isFinite would fix these issues  Keep that in mind when using them      Update    Here s how jQuery does it now  2 2-stable     isNumeric  function obj        var realStringObj   obj  amp  amp  obj toString        return  jQuery isArray obj   amp  amp   realStringObj - parseFloat realStringObj    1   gt   0      Update   Angular 4 3   export function isNumeric value  any   boolean       return  isNaN value - parseFloat value

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Well  I m using this one I made     It s been working so far   function checkNumber value        if   value   1    0           return true      else         return false      If you spot any problem with it  tell me  please   Like any numbers should be divisible by one with nothing left  I figured I could just use the module  and if you try dividing a string into a number the result wouldn t be that  So

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The following may work as well   function isNumeric v             return v length  gt  0  amp  amp   isNaN v   amp  amp  v search   A-Z      ig     -1

[javascript] Validate decimal numbers in JavaScript - IsNumeric()

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