Get number of digits with JavaScript

Question

As the title of my post suggests  I would like to know how many digits var number has  For example  If number   15  my function should return 2  Currently  it looks like this   function getlength number      return number toString   length        But Safari says it is not working due to a TypeError    2  is not a function  evaluating  number toString   length       As you can see   2  is actually the right solution  But why is it not a function

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Note   This function will ignore the numbers after the decimal mean dot  If you wanna count with decimal then remove the Math floor    Direct to the point check this out   function digitCount   num          return Math floor  num toString    length      digitCount 2343         ES5    const digitCount2   num   gt  String  Math floor  Math abs num      length    console log digitCount2 3343     Basically What s going on here  toString   and String   same build-in function for converting digit to string  once we converted then we ll find the length of the string by build-in function length    Alert  But this function wouldn t work properly for negative number  if you re trying to play with negative number then check this answer Or simple put Math abs   in it   Cheer You

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Since this came up on a Google search for  javascript get number of digits   I wanted to throw it out there that there is a shorter alternative to this that relies on internal casting to be done for you   var int number   254  var int length       int number  length   var dec number   2 12  var dec length       dec number  length   console log int length  dec length     Yields  3 4

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Here is my solution  It works with positive and negative numbers  Hope this helps  function findDigitAmount num        var positiveNumber   Math sign num    num     var lengthNumber   positiveNumber toString      return lengthNumber length       findDigitAmount -96456431         8  findDigitAmount 1524              4

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Problem statement  Count number string not using string length   jsfunction  Solution  we could do this through the Forloop  e g  for  x 0  y gt  1   y y  10     x       if  x  lt   10      this y   this number                        else    this number   this y

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Two digits  simple function in case you need two or more digits of a number with ECMAScript 6  ES6    const zeroDigit   num   gt  num toString   length     1    0  num     num

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length is a property  not a method  You can t call it  hence you don t need parenthesis      function getlength number        return number toString   length      UPDATE  As discussed in the comments  the above example won t work for float numbers  To make it working we can either get rid of a period with String number  replace          length  or count the digits with regular expression  String number  match   d g  length   In terms of speed potentially the fastest way to get number of digits in the given number is to do it mathematically  For positive integers there is a wonderful algorithm with log10   var length   Math log number    Math LOG10E   1   0      for positive integers   For all types of integers  including negatives  there is a brilliant optimised solution from  Mwr247  but be careful with using Math log10  as it is not supported by many legacy browsers  So replacing Math log10 x  with Math log x    Math LOG10E will solve the compatibility problem   Creating fast mathematical solutions for decimal numbers won t be easy due to well known behaviour of floating point math  so cast-to-string approach will be more easy and fool proof  As mentioned by  streetlogics fast casting can be done with simple number to string concatenation  leading the replace solution to be transformed to   var length    number       replace          length      for floats

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You can do it by simple loop using Math trunc   function  if in interview interviewer ask to do it without converting it into string      let num   555194154234       let len   0       const numLen    num    gt         for let i   0  i  lt  num     num    1   i             num   Math trunc num 10           len                  return len   1             console log numLen num

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you can use the Math abs function to turn negative numbers to positive and keep positives as it is  then you can convert the number to string and provide length  look at this function  const digitCount   num   gt  Math abs num  toString   length   i found this method the easiest and it works pretty good

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Please use the following expression to get the length of the number  length   variableName toString   length

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Here s a mathematical answer  also works for negative numbers    function numDigits x      return Math max Math floor Math log10 Math abs x     0    1      And an optimized version of the above  more efficient bitwise operations    function numDigits x      return  Math log10  x    x  gt  gt  31   -  x  gt  gt  31     0    1      Essentially  we start by getting the absolute value of the input to allow negatives values to work correctly  Then we run the through the log10 operation to give us what power of 10 the input is  if you were working in another base  you would use the logarithm for that base   which is the number of digits  Then we floor the output to only grab the integer part of that  Finally  we use the max function to fix decimal values  any fractional value between 0 and 1 just returns 1  instead of a negative number   and add 1 to the final output to get the count   The above assumes  based on your example input  that you wish to count the number of digits in integers  so 12345   5  and thus 12345 678   5 as well   If you would like to count the total number of digits in the value  so 12345 678   8   then add this before the  return  in either function above   x   Number String x  replace    0-9  g

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You can use in this trick      number  length

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I m still kind of learning Javascript but I came up with this function in C awhile ago  which uses math and a while loop rather than a string so I re-wrote it for Javascript  Maybe this could be done recursively somehow but I still haven t really grasped the concept    This is the best I could come up with  I m not sure how large of numbers it works with  it worked when I put in a hundred digits   function count digits n        numDigits   0      integers   Math abs n        while  integers  gt  0            integers    integers - integers   10    10          numDigits              return numDigits      edit  only works with integer values

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A solution that also works with both negative numbers and floats  and doesn t call any expensive String manipulation functions  function getDigits n       var a   Math abs n                 take care of the sign    var b   a  lt  lt  0                     truncate the number    if b - a     0                     if the number is a float        return   quot  quot    a  length - 1     return the amount of digits  amp  account for the dot      else          return   quot  quot    a  length         return the amount of digits

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var i   1  while    n    10    gt   1    i             23432          i   1  2343 2        i   2   234 32       i   3    23 432      i   4     2 3432     i   5     0 23432

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for interger digit we can also implement continuously dividing by 10    x000D   x000D  var getNumberOfDigits   function num       var count   1      while Math floor num 10   gt   1           num   Math floor num 10             count            return count     console log getNumberOfDigits 1   console log getNumberOfDigits 12   console log getNumberOfDigits 123   x000D   x000D   x000D

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If you need digits  after separator   you can simply split number and count length second part  after point    function countDigits number        var sp    number       split           if  sp 1      undefined            return sp 1  length        else           return 0

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it would be simple to get the length as        NUM   length   where NUM is the number to get the length for

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The length property returns the length of a string  number of characters    The length of an empty string is 0   var str    Hello World    var n   str length    The result of n will be  12      var str           var n   str length    The result of n will be  0       Array length Property      The length property sets or returns the number of elements in an array   var fruits     Banana    Orange    Apple    Mango    fruits length    The result will be  4  Syntax   Return the length of an array   array length   Set the length of an array   array length number

[javascript] Get number of digits with JavaScript

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