Truncate number to two decimal places without rounding

Question

Suppose I have a value of 15 7784514  I want to display it 15 77 with no rounding   var num   parseFloat 15 7784514   document write num toFixed 1    lt br   gt     document write num toFixed 2    lt br   gt     document write num toFixed 3    lt br   gt     document write num toFixed 10      Results in -  15 8 15 78 15 778 15 7784514000    How do I display 15 77

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I fixed using following simple way-  var num   15 7784514  Math floor num 100  100    Results will be 15 77

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If you exactly wanted to truncate to 2 digits of precision  you can go with a simple logic  function myFunction number      var roundedNumber   number toFixed 2     if  roundedNumber  gt  number            roundedNumber   roundedNumber - 0 01        return roundedNumber

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My version for positive numbers   function toFixed norounding n p        var result   n toFixed p       return result  lt   n   result   result - Math pow 0 1 p   toFixed p       Fast  pretty  obvious   version for positive numbers

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Gumbo s second solution  with the regular expression  does work but is slow because of the regular expression   Gumbo s first solution fails in certain situations due to imprecision in floating points numbers   See the JSFiddle for a demonstration and a benchmark   The second solution takes about 1636 nanoseconds per call on my current system  Intel Core i5-2500 CPU at 3 30 GHz   The solution I ve written involves adding a small compensation to take care of floating point imprecision   It is basically instantaneous  i e  on the order of nanoseconds   I clocked 2 nanoseconds per call but the JavaScript timers are not very precise or granular   Here is the JS Fiddle and the code   function toFixedWithoutRounding  value  precision        var factorError   Math pow 10  14       var factorTruncate   Math pow 10  14 - precision       var factorDecimal   Math pow 10  precision       return Math floor Math floor value   factorError   1    factorTruncate    factorDecimal     var values    1 1299999999  1 13  1 139999999  1 14  1 14000000001  1 13   100    for  var i   0  i  lt  values length  i          var value   values i       console log value     -- gt      toFixedWithoutRounding value  2       for  var i   0  i  lt  values length  i          var value   values i       console log value     -- gt      toFixedWithoutRounding value  4       console log  type of result is     typeof toFixedWithoutRounding 1 13   100   100  2        Benchmark var value   1 13   100  var startTime   new Date    var numRun   1000000  var nanosecondsPerMilliseconds   1000000   for  var run   0  run  lt  numRun  run        toFixedWithoutRounding value  2    var endTime   new Date    var timeDiffNs   nanosecondsPerMilliseconds    endTime - startTime   var timePerCallNs   timeDiffNs   numRun  console log  Time per call  nanoseconds       timePerCallNs

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Already there are some suitable answer with regular expression and arithmetic calculation  you can also try this   function myFunction         var str   12 234556       str   str toString   split           var res   str 1  slice 0  2       document getElementById  demo   innerHTML   str 0      res        output  12 23

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I used  num-0 05  toFixed 1  to get the second decimal floored

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Roll your own toFixed function  for positive values Math floor works fine    function toFixed num  fixed        fixed   fixed    0      fixed   Math pow 10  fixed       return Math floor num   fixed    fixed      For negative values Math floor is round of the values  So you can use Math ceil instead   Example    Math ceil -15 778665   10000    10000   -15 7786 Math floor -15 778665   10000    10000   -15 7787    wrong

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const toFixed    value    gt  value toString   slice 0 5

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I opted to write this instead to manually remove the remainder with strings so I don t have to deal with the math issues that come with numbers   num   num toString      If it s not already a String num   num slice 0   num indexOf       3     With 3 exposing the hundredths place Number num     If you need it back as a Number   This will give you  15 77  with num   15 7784514

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The following code works very good for me    num toString   match          0 2        0

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Another single-line solution   number   Math trunc number 100  100  I used 100 because you want to truncate to the second digit  but a more flexible solution would be   number   Math trunc number Math pow 10  digits   Math pow 10  digits   where digits is the amount of decimal digits to keep  See Math trunc specs for details and browser compatibility

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These solutions do work  but to me seem unnecessarily complicated   I personally like to use the modulus operator to obtain the remainder of a division operation  and remove that   Assuming that num   15 7784514   num- num  01    This is equivalent to saying num   num -  num    01

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An Easy way to do it is the next but is necessary ensure that the amount parameter is given as a string     function truncate amountAsString  decimals   2     var dotIndex   amountAsString indexOf         var toTruncate   dotIndex     -1   amp  amp    amountAsString length  gt  dotIndex   decimals   1     var approach   Math pow 10  decimals     var amountToTruncate   toTruncate   amountAsString slice 0  dotIndex   decimals  1    amountAsString      return toTruncate        Math floor parseFloat amountToTruncate    approach     approach        parseFloat amountAsString        console log truncate  7 99999       OUTPUT    gt  7 99 console log truncate  7 99999   3      OUTPUT    gt  7 999 console log truncate  12 799999999999999       OUTPUT    gt  7 99

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I know there are already few working examples  but I  think it s worth to propose my String toFixed equivalent  some may find it helpful   That s my toFixed alternative  that don t round numbers  just truncates it or adds zeroes according to given precision  For extra long number it uses JS build-in rounding when precision is to long  Function works for all problematic number I ve found on stack   function toFixedFixed value  precision   0        let stringValue   isNaN  value     0    String  value        if  stringValue indexOf  e    gt  -1    stringValue      Infinity     stringValue      -Infinity             throw new Error  To large number to be processed               let   beforePoint  afterPoint     stringValue indexOf       gt  -1   stringValue split          stringValue               Force automatic rounding for some long real numbers that ends with 99X  by converting it to string  cutting off last digit  then adding extra nines and casting it on number again        e g  2 0199999999999996     2 019999999999999     9999   will give 2 02     if  stringValue length  gt   17  amp  amp  afterPoint length  gt  2  amp  amp   afterPoint substr afterPoint length - 3   gt  995            stringValue   String   stringValue substr 0  afterPoint length - 1     9  repeat stringValue split      shift   length   4               beforePoint  afterPoint     String stringValue  indexOf       gt  -1   stringValue split          stringValue                  if  precision     0            return beforePoint        else if  afterPoint length  gt  precision            return    beforePoint    afterPoint substr 0  precision           else           return    beforePoint    afterPoint    0  repeat precision - afterPoint length               Keep in mind that precision may not be handled properly for numbers of length 18 and greater  e g  64-bit Chrome will round it or add  e      e-  to keep number s length at 18   If you want to perform operations on real numbers it s safer to multiply it by Math sqrt 10  precision  first  make the calculations  then dive result by multiplier s value   Example       0 06   0 01 is 0 06999999999999999  and every formatting function   that s not rounding will truncate it to 0 06 for precision 2       But if you ll perform same operation with multiplier amp divider   0 06   100   0 01   100    100  you ll get 0 07    That s why it s so important to use such multiplier divider when dealing with real numbers in javascript  especially when you re calculating money

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Building on David D s answer   function NumberFormat num n      var num    arguments 0     null    arguments 0    0    var n    arguments 1     null    arguments 1    2    if num  gt  0       num   String num       if num indexOf          -1          var numarr   num split             if  numarr length  gt  1            if n  gt  0             var temp   numarr 0                   for var i   0  i  lt  n  i                 if i  lt  numarr 1  length                 temp    numarr 1  charAt i                                       num   Number temp                                 return Number num      console log  NumberFormat 123 85 2   NumberFormat 123 85 2    console log  NumberFormat 123 851 2   NumberFormat 123 851 2    console log  NumberFormat 0 85 2   NumberFormat 0 85 2    console log  NumberFormat 0 851 2   NumberFormat 0 851 2    console log  NumberFormat 0 85156 2   NumberFormat 0 85156 2    console log  NumberFormat 0 85156 4   NumberFormat 0 85156 4    console log  NumberFormat 0 85156 8   NumberFormat 0 85156 8    console log  NumberFormat   85156  2   NumberFormat   85156  2    console log  NumberFormat  0 85156  2   NumberFormat  0 85156  2    console log  NumberFormat  1005 85156  2   NumberFormat  1005 85156  2    console log  NumberFormat  0  2   NumberFormat  0  2    console log  NumberFormat    2   NumberFormat    2    console log  NumberFormat 85156 8   NumberFormat 85156 8    console log  NumberFormat  85156  2   NumberFormat  85156  2    console log  NumberFormat  85156   2   NumberFormat  85156   2        NumberFormat 123 85 2  123 85    NumberFormat 123 851 2  123 85    NumberFormat 0 85 2  0 85    NumberFormat 0 851 2  0 85    NumberFormat 0 85156 2  0 85    NumberFormat 0 85156 4  0 8515    NumberFormat 0 85156 8  0 85156    NumberFormat   85156  2  0 85    NumberFormat  0 85156  2  0 85    NumberFormat  1005 85156  2  1005 85    NumberFormat  0  2  0    NumberFormat    2  0    NumberFormat 85156 8  85156    NumberFormat  85156  2  85156    NumberFormat  85156   2  85156

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Update 5 Nov 2016  New answer  always accurate  function toFixed num  fixed        var re   new RegExp   -   d        d 0      fixed    -1                return num toString   match re  0       As floating point math in javascript will always have edge cases  the previous solution will be accurate most of the time which is not good enough  There are some solutions to this like num toPrecision  BigDecimal js  and accounting js  Yet  I believe that merely parsing the string will be the simplest and always accurate   Basing the update on the well written regex from the accepted answer by  Gumbo  this new toFixed function will always work as expected     Old answer  not always accurate   Roll your own toFixed function   function toFixed num  fixed        fixed   fixed    0      fixed   Math pow 10  fixed       return Math floor num   fixed    fixed

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The most efficient solution  for 2 fraction digits  is to subtract 0 005 before calling toFixed    function toFixed2  num     return  num-0 005  toFixed 2      Negative numbers will be rounded down too  away from zero   The OP didn t tell anything about negative numbers

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parseInt is faster then Math floor  function floorFigure figure  decimals       if   decimals  decimals   2      var d   Math pow 10 decimals       return  parseInt figure d  d  toFixed decimals       floorFigure 123 5999       gt     123 59  floorFigure 123 5999  3    gt     123 599

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x000D   x000D  function formatLimitDecimals value  decimals    x000D    value   value toString   split      x000D   x000D    if  value length     2    x000D      return Number  value 0   value 1  slice 0  decimals   join       x000D      else   x000D      return Number value 0    x000D      x000D    x000D   x000D  console log formatLimitDecimals 4 156  2       4 15 x000D  console log formatLimitDecimals 4 156  8       4 156 x000D  console log formatLimitDecimals 4 156  0       4 x000D   x000D   x000D

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Another solution  that truncates and round   function round  number  decimals  truncate        if  truncate            number   number toFixed decimals   1           return parseFloat number slice 0  -1               var n   Math pow 10 0  decimals       return Math round number   n    n

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Simple do this  number   parseInt number   100  100

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num   19 66752 f   num toFixed 3  slice 0 -1  alert f    This will return 19 66

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Update  Jan 2021  Depending on its range  a number in javascript may be shown in scientific notation  For example  if you type 0 0000001 in the console  you may see it as 1e-7  whereas 0 000001 appears unchanged  0 000001   If your application works on a range of numbers for which scientific notation is not involved  you can just ignore this update and use the original answer below   This update is about adding a function that checks if the number is in scientific format and  if so  converts it into decimal format  Here I m proposing this one  but you can use any other function that achieves the same goal  according to your application s needs  function toFixed x      if  Math abs x   lt  1 0        var e   parseInt x toString   split  e-   1        if  e            x    Math pow 10 e-1           x    0      new Array e   join  0     x toString   substring 2             else       var e   parseInt x toString   split      1        if  e  gt  20            e -  20          x    Math pow 10 e           x     new Array e 1   join  0                return x     Now just apply that function to the parameter  that s the only change with respect to the original answer   function toFixedTrunc x  n          x   toFixed x             From here on the code is the same than the original answer       const v    typeof x      string    x   x toString    split             if  n  lt   0  return v 0         let f   v 1               if  f length  gt  n  return    v 0     f substr 0 n           while  f length  lt  n  f     0         return    v 0     f          This updated version addresses also a case mentioned in a comment  toFixedTrunc 0 000000199  2    gt   quot 0 00 quot    Again  choose what fits your application needs at best  Original answer  October 2017  General solution to truncate  no rounding  a number to the n-th decimal digit and convert it to a string with exactly n decimal digits  for any n 0  function toFixedTrunc x  n      const v    typeof x      string    x   x toString    split         if  n  lt   0  return v 0     let f   v 1           if  f length  gt  n  return    v 0     f substr 0 n       while  f length  lt  n  f     0     return    v 0     f      where x can be either a number  which gets converted into a string  or a string  Here are some tests for n 2  including the one requested by OP   0             gt  0 00 0 01          gt  0 01 0 5839        gt  0 58 0 999         gt  0 99 1 01          gt  1 01 2             gt  2 00 2 551         gt  2 55 2 99999       gt  2 99 4 27          gt  4 27 15 7784514    gt  15 77 123 5999      gt  123 59  And for some other values of n  15 001097     gt  15 0010  n 4  0 000003298   gt  0 0000032  n 7  0 000003298257899   gt  0 000003298257  n 12

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This worked well for me  I hope it will fix your issues too    function toFixedNumber number        const spitedValues   String number toLocaleString    split           let decimalValue   spitedValues length  gt  1   spitedValues 1            decimalValue   decimalValue concat  00   substr 0 2        return     spitedValues 0          decimalValue        5 56789      ---- gt    5 56    0 342        ---- gt    0 34    -10 3484534  ---- gt    -10 34     600          ---- gt    600 00    x000D   x000D  function convertNumber    x000D    var result   toFixedNumber document getElementById  valueText   value   x000D    document getElementById  resultText   value   result  x000D    x000D   x000D   x000D  function toFixedNumber number    x000D          const spitedValues   String number toLocaleString    split       x000D          let decimalValue   spitedValues length  gt  1   spitedValues 1        x000D          decimalValue   decimalValue concat  00   substr 0 2   x000D   x000D          return     spitedValues 0          decimalValue  x000D    x000D   lt div gt  x000D     lt input type  text  id  valueText  placeholder  Input value here    gt  x000D     lt br gt  x000D     lt button onclick  convertNumber     gt Convert lt  button gt  x000D     lt br gt  lt hr gt  x000D     lt input type  text  id  resultText  placeholder  result  readonly  true  gt  x000D   lt  div gt  x000D   x000D   x000D

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All these answers seem a bit complicated  I would just subtract 0 5 from your number and use toFixed

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It s more reliable to get two floating points without rounding   Reference Answer   x000D   x000D  var number   10 5859  x000D  var fixed2FloatPoints   parseInt number   100    100  x000D  console log fixed2FloatPoints   x000D   x000D   x000D    Thank You

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Here is another one variant to save  toFixed  digits   functional without rounding float variable   Number prototype toRealFixed   function digits        return Math floor this valueOf     Math pow 10  digits     Math pow 10  digits        And calling   var float var   0 02209062  float var toRealFixed

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The answers here didn t help me  it kept rounding up or giving me the wrong decimal   my solution converts your decimal to a string  extracts the characters and then returns the whole thing as a number    function Dec2 num      num   String num     if num indexOf          -1        var numarr   num split           if  numarr length    1          return Number num             else         return Number numarr 0      numarr 1  charAt 0  numarr 1  charAt 1                else       return Number num            Dec2 99      99 Dec2 99 9999999      99 99 Dec2 99 35154      99 35 Dec2 99 8      99 8 Dec2 10265 985475      10265 98

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My solution in typescript  can easily be ported to JS           Returns the price with correct precision as a string        param   price The price in decimal to be formatted      param   decimalPlaces The number of decimal places to use     return  string The price in Decimal formatting      type toDecimal    price  number  decimalPlaces   number    gt  string  const toDecimalOdds  toDecimal       price  number    decimalPlaces  number   2     string   gt      const priceString  string   price toString      const pointIndex  number   priceString indexOf             Return the integer part if decimalPlaces is 0   if  decimalPlaces     0        return priceString substr 0  pointIndex             Return value with 0s appended after decimal if the price is an integer   if  pointIndex     -1        const padZeroString  string    0  repeat decimalPlaces        return    priceString    padZeroString              If numbers after decimal are less than decimalPlaces  append with 0s   const padZeroLen  number   priceString length - pointIndex - 1    if  padZeroLen  gt  0  amp  amp  padZeroLen  lt  decimalPlaces        const padZeroString  string    0  repeat padZeroLen        return    priceString   padZeroString           return priceString substr 0  pointIndex   decimalPlaces   1        Test cases     expect filters toDecimalOdds 3 14159   toBe  3 14      expect filters toDecimalOdds 3 14159  2   toBe  3 14      expect filters toDecimalOdds 3 14159  0   toBe  3      expect filters toDecimalOdds 3 14159  10   toBe  3 1415900000      expect filters toDecimalOdds 8 2   toBe  8 20      Any improvements

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Taking the knowledge from all the previous answers combined   this is what I came up with as a solution   function toFixedWithoutRounding num  fractionDigits      if   num  gt  0  amp  amp  num  lt  0 000001      num  lt  0  amp  amp  num  gt  -0 000001            HACK  below this js starts to turn numbers into exponential form like 1e-7         This gives wrong results so we are just changing the original number to 0 here        as we don t need such small numbers anyway      num   0        const re   new RegExp   -   d        d 0      fractionDigits    -1              return Number num toString   match re  0   toFixed fractionDigits

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Convert the number into a string  match the number up to the second decimal place    x000D   x000D  function calc theform    x000D      var num   theform original value  rounded   theform rounded x000D      var with2Decimals   num toString   match   -  d       d 0 2      0  x000D      rounded value   with2Decimals x000D    x000D   lt form onsubmit  return calc this   gt  x000D  Original number   lt input name  original  type  text  onkeyup  calc form   onchange  calc form     gt  x000D   lt br   gt  Rounded  number   lt input name  rounded  type  text  placeholder  readonly  readonly gt  x000D   lt  form gt  x000D   x000D   x000D    The toFixed method fails in some cases unlike toString  so be very careful with it

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Just truncate the digits   function truncDigits inputNumber  digits      const fact   10    digits    return Math floor inputNumber   fact    fact

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Thanks Martin Varmus  function floorFigure figure  decimals        if   decimals  decimals   2       var d   Math pow 10 decimals        return   figure d  d  toFixed decimals       floorFigure 123 5999       gt     123 59  floorFigure 123 5999  3    gt     123 599    I make a simple update and I got proper rounding  The update is following line  return   figure d  d  toFixed decimals     remove parseInt   function

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Here you are  An answer that shows yet another way to solve the problem          For the sake of simplicity  here is a complete function  function truncate numToBeTruncated  numOfDecimals        var theNumber   numToBeTruncated toString        var pointIndex   theNumber indexOf           return   theNumber slice 0  pointIndex  gt  -1     numOfDecimals   pointIndex   undefined        Note the use of   before the final expression  That is to convert our truncated  sliced string back to number type   Hope it helps

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function toFixed num  fixed        fixed   fixed    0      var front   Math floor num       var back   0      for  var i   1  i  lt   fixed  i              var value   Math floor num   Math pow 10  i     10          back    value   Math pow 10  i             return front   back

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Here is what is did it with string  export function withoutRange number      const str   String number     const dotPosition   str indexOf         if  dotPosition  gt  0        const length   str substring   length      const end   length  gt  3   3   length      return str substring 0  dotPosition   end         return str

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truncate without zeroes  function toTrunc value n         return Math floor value Math pow 10 n    Math pow 10 n        or  function toTrunc value n       x  value toString     0   split           return parseFloat x 0      x 1  substr 0 n        test   toTrunc 17 4532 2     17 45 toTrunc 177 4532 1    177 4 toTrunc 1 4532 1      1 4 toTrunc  4 2          0 4   truncate with zeroes  function toTruncFixed value n       return toTrunc value n  toFixed n       test   toTrunc 17 4532 2     17 45 toTrunc 177 4532 1    177 4 toTrunc 1 4532 1      1 4 toTrunc  4 2          0 40

[javascript] Truncate number to two decimal places without rounding

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