How do you round to 1 decimal place in Javascript

Question

Can you round a number in javascript to 1 character after the decimal point  properly rounded    I tried the  10  round   10 but it leaves two decimals at the end of the int

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Math round  num   10    10 doesn t work   For example  1455581777 8-145558160 4 gives you 1310023617 3999999   So only use num toFixed 1

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Math round num   10    10 works  here is an example     var number   12 3456789 var rounded   Math round number   10    10    rounded is 12 3   if you want it to have one decimal place  even when that would be a 0  then add     var fixed   rounded toFixed 1     fixed is always to 1 d p     NOTE   toFixed   returns a string      To convert back to number format parseFloat number toFixed 2      12 34    but that will not retain any trailing zeros     So  just make sure it is the last step before output     and use a number format during calculations    EDIT  Add round with precision function     Using this principle  for reference  here is a handy little round function that takes precision     function round value  precision        var multiplier   Math pow 10  precision    0       return Math round value   multiplier    multiplier          usage      round 12345 6789  2     12345 68 round 12345 6789  1     12345 7       defaults to round to nearest whole number  precision 0       round 12345 6789     12346       and can be used to round to nearest 10 or 100 etc     round 12345 6789  -1     12350 round 12345 6789  -2     12300       and correct handling of negative numbers      round -123 45  1     -123 4 round 123 45  1     123 5       and can be combined with toFixed to format consistently as string      round 456 7  2  toFixed 2      456 70

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If your method does not work  plz post your code   However you could accomplish the rounding off task as   var value   Math round 234 567 100  100   Will give you 234 56  Similarly   var value   Math round 234 567 10  10   Will give 234 5  In this way you can use a variable in the place of the constant as used above

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Using toPrecision method   var a   1 2345 a toPrecision 2      result  1 2

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I made one that returns number type and also places decimals only if are needed  no 0 padding   Examples  roundWithMaxPrecision 11 234  2     11 23 roundWithMaxPrecision 11 234  1     11 2 roundWithMaxPrecision 11 234  4     11 23 roundWithMaxPrecision 11 234  -1     10  roundWithMaxPrecision 4 2  2     4 2 roundWithMaxPrecision 4 88  1     4 9  The code  function roundWithMaxPrecision  n  precision        let precisionWithPow10   Math pow 10  precision       return Math round n   precisionWithPow10    precisionWithPow10

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In general  decimal rounding is done by scaling  round num   p    p Naive implementation Using the following function with halfway numbers  you will get either the upper rounded value as expected  or the lower rounded value sometimes depending on the input  This inconsistency in rounding may introduce hard to detect bugs in the client code   x000D   x000D  function naiveRound num  decimalPlaces        var p   Math pow 10  decimalPlaces       return Math round num   p    p     console log  naiveRound 1 245  2         1 25 correct  rounded as expected  console log  naiveRound 1 255  2         1 25 incorrect  should be 1 26  x000D   x000D   x000D   Better implementations By converting the number to a string in the exponential notation  positive numbers are rounded as expected  But  be aware that negative numbers round differently than positive numbers  In fact  it performs what is basically equivalent to  quot round half up quot  as the rule  you will see that round -1 005  2  evaluates to -1 even though round 1 005  2  evaluates to 1 01  The lodash   round method uses this technique   x000D   x000D         Round half up   round half towards positive infinity      Uses exponential notation to avoid floating-point issues     Negative numbers round differently than positive numbers      function round num  decimalPlaces        num   Math round num    e    decimalPlaces       return Number num    e    -decimalPlaces         test rounding of half console log  round 0 5  0         1 console log  round -0 5  0        0     testing edge cases console log  round 1 005  2          1 01 console log  round 2 175  2          2 18 console log  round 5 015  2          5 02  console log  round -1 005  2         -1 console log  round -2 175  2         -2 17 console log  round -5 015  2         -5 01 x000D   x000D   x000D   If you want the usual behavior when rounding negative numbers  you would need to convert negative numbers to positive before calling Math round    and then convert them back to negative numbers before returning     Round half away from zero function round num  decimalPlaces        num   Math round Math abs num     quot e quot    decimalPlaces    Math sign num       return Number num    quot e quot    -decimalPlaces      There is a different purely mathematical technique to perform round-to-nearest  using  quot round half away from zero quot    in which epsilon correction is applied before calling the rounding function  Simply  we add the smallest possible float value    1 0 ulp  unit in the last place  to the number before rounding  This moves to the next representable value after the number  away from zero   x000D   x000D         Round half away from zero   commercial  rounding     Uses correction to offset floating-point inaccuracies     Works symmetrically for positive and negative numbers      function round num  decimalPlaces        var p   Math pow 10  decimalPlaces       var e   Number EPSILON   num   p      return Math round  num   p    e    p        test rounding of half console log  round 0 5  0         1 console log  round -0 5  0        -1     testing edge cases console log  round 1 005  2         1 01 console log  round 2 175  2         2 18 console log  round 5 015  2         5 02  console log  round -1 005  2        -1 01 console log  round -2 175  2        -2 18 console log  round -5 015  2        -5 02 x000D   x000D   x000D   This is needed to offset the implicit round-off error that may occur during encoding of decimal numbers  particularly those  having  quot 5 quot  in the last decimal position  like 1 005  2 675 and 16 235  Actually  1 005 in decimal system is encoded to 1 0049999999999999 in 64-bit binary float  while  1234567 005 in decimal system is encoded to 1234567 0049999998882413 in 64-bit binary float  It is worth noting that the maximum binary round-off error is dependent upon  1  the magnitude of the number and  2  the relative machine epsilon  2 -52

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var number   123 456   console log number toFixed 1       should round to 123 5

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I vote for toFixed    but  for the record  here s another way that uses bit shifting to cast the number to an int   So  it always rounds towards zero  down for positive numbers  up for negatives    var rounded     num   10   lt  lt  0    0 1    But hey  since there are no function calls  it s wicked fast      And here s one that uses string matching   var rounded    num       replace        d      d         1 2      I don t recommend using the string variant  just sayin

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ES 6 Version of Accepted Answer   function round value  precision        const multiplier   10     precision    0       return Math round value   multiplier    multiplier

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function rnd v n 2        return Math round  v Number EPSILON  Math pow 10 n   Math pow 10 n     this one catch the corner cases well

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I found a way to avoid the precision problems   function badRound  num  precision        const x   10    precision      return Math round num   x    x      badRound 1 005  2  -- gt  1  function round  num  precision        const x   10     precision   1       const y   10    precision      return Math round Math round num   x    10    y      round 1 005  2  -- gt  1 01

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Why not just  let myNumber   213 27321   myNumber toFixed 1        gt  213 3    toFixed  returns a string representing the given number using fixed-point notation  Unary plus      The unary plus operator precedes its operand and evaluates to its operand but attempts to convert it into a number  if it isn t already

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This seems to work reliably across anything I throw at it   function round val  multiplesOf      var s   1   multiplesOf    var res   Math ceil val s  s    res   res  lt  val   res   multiplesOf  res    var afterZero   multiplesOf toString   split      1     return parseFloat res toFixed afterZero   afterZero length   0        It rounds up  so you may need to modify it according to use case  This should work   console log round 10 01  1      outputs 11 console log round 10 01  0 1      outputs 10 1

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Math round  mul count   10     10  Math round Math sqrt sqD y    10     10   Thanks

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var num   34 7654   num   Math round num   10    10   console log num      Logs  34 8

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lodash has a round method     round 4 006        gt  4    round 4 006  2        gt  4 01    round 4060  -2        gt  4100   Docs   Source

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To complete the Best Answer   var round   function   number  precision         precision   precision    0      return parseFloat  parseFloat  number   toFixed  precision          The input parameter number may  not  always be a number  in this case  toFixed does not exist

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If your source code is typescript you could use a function like this  public static ToFixedRounded decimalNumber  number  fractionDigits  number   number       var rounded   Math pow 10  fractionDigits       return  Math round decimalNumber   rounded    rounded  toFixed fractionDigits  as unknown as number

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Try with this   var original 28 453     1 - round  original  to two decimals var result   Math round  original   100    100    returns 28 45     2 - round  original  to 1 decimal var result   Math round  original   10    10    returns 28 5     3 - round 8 111111 to 3 decimals var result   Math round  8 111111   1000    1000    returns 8 111   less complicated and easier to implement     with this  you can create a function to do   function RoundAndFix  n  d        var m   Math pow  10  d       return Math round  n   m    m       x000D   x000D  function RoundAndFix  n  d    x000D      var m   Math pow  10  d   x000D      return Math round  n   m    m  x000D    x000D  console log  RoundAndFix 8 111111  3    x000D   x000D   x000D    EDIT  see this How to round using ROUND HALF UP  Rounding mode that most of us were taught in grade school

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If you care about proper rounding up then   function roundNumericStrings str   numOfDecPlacesRequired         var roundFactor   Math pow 10  numOfDecPlacesRequired          return  Math round parseFloat str  roundFactor  roundFactor  toString           Else if you don t then you already have a reply from previous posts  str slice 0  -1

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Little Angular filter if anyone wants it   angular module  filters   filter  decimalPlace   function         return function num  precision            var multiplier   Math pow 10  precision    0           return Math round num   multiplier    multiplier               use if via     model value  decimalPlace     model value  decimalPlace 1     model value  decimalPlace 2

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If you use Math round 5 01  you will get 5 instead of 5 0   If you use toFixed you run into rounding issues   If you want the best of both worlds combine the two    Math round 5 01   10    10  toFixed 1    You might want to create a function for this   function roundedToFixed  float   digits     var rounded   Math pow 10   digits     return  Math round  float   rounded    rounded  toFixed  digits

[javascript] How do you round to 1 decimal place in Javascript?

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