Check if a number has a decimal place is a whole number

Question

I am looking for an easy way in JavaScript to check if a number has a decimal place in it  in order to determine if it is an integer    For instance   23 - gt  OK 5 - gt  OK 3 5 - gt  not OK 34 345 - gt  not OK   if number is integer

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You can multiply it by 10 and then do a  modulo  operation divison with 10  and check if result of that two operations is zero  Result of that two operations will give you first digit after the decimal point  If result is equal to zero then the number is a whole number   if    int  number   10 0    10    0       your code

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function isWholeNumber num      return num     Math round num

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Using modulus will work   num   1    0    23   1   0    23 5   1   0 5     Note that this is based on the numerical value of the number  regardless of format  It treats numerical strings containing whole numbers with a fixed decimal point the same as integers    10 0    1     returns 0 10   1     returns 0  10 5    1     returns 0 5 10 5   1     returns 0 5

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Simple  but effective   Math floor number      number

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parseInt num      num   when passed a number  parseInt   just returns the number as int   parseInt 3 3      3 3    false because 3     3 3 parseInt 3      3        true

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function isDecimal n       if n                return false       var strCheck    0123456789       var i       for i in n           if strCheck indexOf n i      -1              return false            return true

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Use following if value is string  e g  from  lt input    Math floor value  toString       value   I add  toString   to floor to make it work also for cases when value     1    ends with decimal separator or another string   Also Math floor always returns some value so  toString   never fails

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The most common solution is to strip the integer portion of the number and compare it to zero like so   function Test          var startVal   123 456      alert   startVal - Math floor startVal      0

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Function for check number is Decimal or whole number  function IsDecimalExist p decimalNumber        var l boolIsExist   true       if  p decimalNumber   1    0          l boolIsExist   false       return l boolIsExist

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How about byte-ing it   Number prototype isInt  function     return this   this gt  gt  0      I always feel kind of bad for bit operators in javascript-   they hardly get any exercise

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Number isInteger 23       true Number isInteger 1 5      false Number isInteger  x       false     Number isInteger   is part of the ES6 standard and not supported in IE11   It returns false for NaN  Infinity and non-numeric arguments while x   1    0 returns true

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number   20 5  if  number    Math floor number      alert  Integer      else    alert  Decimal        Pretty cool and works for things like XX 0 too  It works because Math floor   chops off any decimal if it has one so if the floor is different from the original number we know it is a decimal  And no string conversions

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function isDecimal num      return  num     parseInt num  10

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convert number string to array  split by decimal point  Then  if the array has only one value  that means no decimal in string   if  number split      1          do stuff     This way you can also know what the integer and decimal actually are  a more advanced example would be   number to array   string split       inte   number to array 0   dece   number to array 1     if  dece         do stuff

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Or you could just use this to find out if it is NOT a decimal   string indexOf         -1

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Perhaps this works for you   It uses regex to check if there is a comma in the number  and if there is not  then it will add the comma and stripe   var myNumber    50   function addCommaStripe text       if     test text     false           return text      -         else           return text          myNumber   addCommaStripe myNumber

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var re   -  0-9      var num 10  re test num

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You can use the bitwise operations that do not change the value    0 or     to discard the decimal part  which can be used for rounding  After rounding the number  it is compared to the original value   function isDecimal num      return  num   0      num     console log  isDecimal 1        false console log  isDecimal 1 5        true console log  isDecimal -0 5        true

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Number isInteger   is probably the most concise  It returns true if it is an integer  and false if it isn t

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Here s an excerpt from my guard library  inspired by Effective JavaScript by David Herman    var guard          guard  function x            if   this test x                 throw new TypeError  expected     this                                           var number   Object create guard   number test   function x        return typeof x      number     x instanceof Number     number toString   function         return  number        var uint32   Object create guard   uint32 test   function x        return typeof x      number   amp  amp  x      x  gt  gt  gt  0      uint32 toString   function         return  uint32        var decimal   Object create guard   decimal test   function x        return number test x   amp  amp   uint32 test x      decimal toString   function         return  decimal        uint32 guard 1234          fine uint32 guard 123 4         TypeError  expected uint32  decimal guard 1234         TypeError  expected decimal decimal guard 123 4        fine

[javascript] Check if a number has a decimal place/is a whole number

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