Decimal or numeric values in regular expression validation

Question

I am trying to use a regular expression validation to check for only decimal values or numeric values  But user enters numeric value  it don t be first digit  0   How do I do that

User · Answer

I had the same problem  but I also wanted   25  to be a valid decimal number   Here is my solution using JavaScript   function isNumber v          0-9   Zero or more digits between 0 and 9   This allows  25 to be considered valid            Matches 0 or 1 things in the parentheses    Allows for an optional decimal point       Decimal point escaped with         If a decimal point does exist  it must be followed by 1 or more digits  0-9        d and  0-9  are equivalent         and   anchor the endpoints so tthe whole string must match    return v trim   length  gt  0  amp  amp  v trim   match    0-9      0-9             Where my trim   method is  String prototype trim   function       return this replace     s   s    g            Matthew DesVoigne

User · Answer

if you need to validate decimal with dots  commas  positives and negatives try this   Object testObject    -1 5   boolean isDecimal   Pattern matches         -  0 1  0-9           1  0-9       CharSequence  testObject     Good luck

User · Answer

A digit in the range 1-9 followed by zero or more other digits     1-9  d     To allow numbers with an optional decimal point followed by digits  A digit in the range 1-9 followed by zero or more other digits then optionally followed by a decimal point followed by at least 1 digit     1-9  d     d       Notes    The   and   anchor to the start and end basically saying that the whole string must match the pattern     matches 0 or 1 of the whole thing between the brackets   Update to handle commas   In regular expressions   has a special meaning - match any single character  To match literally a   in a string you need to escape the   using    This is the meaning of the    in the regexp above  So if you want to use comma instead the pattern is simply     1-9  d    d       Further update to handle commas and full stops  If you want to allow a   between groups of digits and a   between the integral and the fractional parts then try     1-9  d 0 2     d 3      d       i e  this is a digit in the range 1-9 followed by up to 2 other digits then zero or more groups of a full stop followed by 3 digits then optionally your comma and digits as before   If you want to allow a   anywhere between the digits then try     1-9     d     d       i e  a digit 1-9 followed by zero or more digits or full stops optionally followed by a comma and one or more digits

User · Answer

Here is a great working regex for numbers  This accepts number with commas and decimals      -     d   d 1 3      d 3           d

User · Answer

Actually  none of the given answers are fully cover the request  As the OP didn t provided a specific use case or types of numbers  I will try to cover all possible cases and permutations   Regular Numbers  Whole Positive  This number is usually called unsigned integer  but you can also call it a positive non-fractional number  include zero  This includes numbers like 0  1 and 99999  The Regular Expression that covers this validation is      0  1-9  d       Test This Regex  Whole Positive and Negative  This number is usually called signed integer  but you can also call it a non-fractional number  This includes numbers like 0  1  99999  -99999  -1 and -0  The Regular Expression that covers this validation is     -  0  1-9  d       Test This Regex  As you probably noticed  I have also included -0 as a valid number  But  some may argue with this usage  and tell that this is not a real number  you can read more about Signed Zero here   So  if you want to exclude this number from this regex  here s what you should use instead     -  0  1-9  d     lt  -0      Test This Regex  All I have added is    lt  -0   which means not to include -0 before this assertion  This    lt       assertion called negative lookbehind  which means that any phrase replaces the     should not appear before this assertion  Lookbehind has limitations  like the phrase cannot include quantifiers  That s why for some cases I ll be using Lookahead instead  which is the same  but in the opposite way      Many regex flavors  including those used by Perl and Python  only allow fixed-length strings  You can use literal text  character escapes  Unicode escapes other than  X  and character classes  You cannot use quantifiers or backreferences  You can use alternation  but only if all alternatives have the same length  These flavors evaluate lookbehind by first stepping back through the subject string for as many characters as the lookbehind needs  and then attempting the regex inside the lookbehind from left to right    You can read more bout Lookaround assertions here   Fractional Numbers  Positive  This number is usually called unsigned float or unsigned double  but you can also call it a positive fractional number  include zero  This includes numbers like 0  1  0 0  0 1  1 0  99999 000001  5 10  The Regular Expression that covers this validation is      0  1-9  d      d        Test This Regex  Some may say  that numbers like  1   0 and  00651  same as 0 1  0 0 and 0 00651 respectively  are also valid fractional numbers  and I cannot disagree with them  So here is a regex that is additionally supports this format      0  1-9  d       d      lt   d      Test This Regex  Negative and Positive  This number is usually called signed float or signed double  but you can also call it a fractional number  This includes numbers like 0  1  0 0  0 1  1 0  99999 000001  5 10  -0  -1  -0 0  -0 1  -99999 000001  5 10  The Regular Expression that covers this validation is     -  0  1-9  d      d        Test This Regex  For non -0 believers        -0   0     -  0  1-9  d      d        Test This Regex  For those who want to support also the invisible zero representations  like  1  - 1  use the following regex     -  0  1-9  d       d      lt   d      Test This Regex  The combination of non -0 believers and invisible zero believers  use this regex        -0    0     -  0  1-9  d       d      lt   d      Test This Regex  Numbers with a Scientific Notation  AKA Exponential Notation   Some may want to support in their validations  numbers with a scientific character e  which is by the way  an absolutely valid number  it is created for shortly represent a very long numbers  You can read more about Scientific Notation here  These numbers are usually looks like 1e3  which is 1000   1e-3  which is 0 001  and are fully supported by many major programming languages  e g  JavaScript   You can test it by checking if the expression  1e3   1000 returns true  I will divide the support for all the above sections  including numbers with scientific notation     Regular Numbers  Whole positive number regex validation  supports numbers like 6e4  16e-10  0e0 but also regular numbers like 0  11      0  1-9  d   e-  0  1-9  d      i   Test This Regex  Whole positive and negative number regex validation  supports numbers like -6e4  -16e-10  -0e0 but also regular numbers like -0  -11 and all the whole positive numbers above     -  0  1-9  d   e-  0  1-9  d      i   Test This Regex  Whole positive and negative number regex validation for non -0 believers  same as the above  except now it forbids numbers like -0  -0e0  -0e5 and -0e-6        -0 -  0  1-9  d   e-  0  1-9  d      i   Test This Regex  Fractional Numbers  Positive number regex validation  supports also the whole numbers above  plus numbers like 0 1e3  56 0e-3  0 0e10 and 1 010e0      0  1-9  d      d    e-  0  1-9  d      i   Test This Regex  Positive number with invisible zero support regex validation  supports also the above positive numbers  in addition numbers like  1e3   0e0   0e-5 and  1e-7      0  1-9  d       d      lt   d  e-  0  1-9  d      i   Test This Regex  Negative and positive number regex validation  supports the positive numbers above  but also numbers like -0e3  -0 1e0  -56 0e-3 and -0 0e10     -  0  1-9  d      d    e-  0  1-9  d      i   Test This Regex  Negative and positive number regex validation fro non -0 believers  same as the above  except now it forbids numbers like -0  -0 00000  -0 0e0  -0 00000e5 and -0e-6        -0   0    e    -  0  1-9  d      d    e-  0  1-9  d      i   Test This Regex  Negative and positive number with invisible zero support regex validation  supports also the above positive and negative numbers  in addition numbers like - 1e3  - 0e0  - 0e-5 and - 1e-7     -  0  1-9  d       d      lt   d  e-  0  1-9  d      i   Test This Regex  Negative and positive number with the combination of non -0 believers and invisible zero believers  same as the above  but forbids numbers like - 0e0  - 0000e15 and - 0e-19        -0    0    e    -  0  1-9  d       d      lt   d  e-  0  1-9  d      i   Test This Regex  Numbers with Hexadecimal Representation  In many programming languages  string representation of hexadecimal number like 0x4F7A may be easily cast to decimal number 20346  Thus  one may want to support it in his validation script  The following Regular Expression supports only hexadecimal numbers representations     0x 0-9a-f    i   Test This Regex  All Permutations  These final Regular Expressions  support the invisible zero numbers   Signed Zero Believers     -  0  1-9  d       d      lt   d  e-  0  1-9  d     0x 0-9a-f     i   Test This Regex  Non Signed Zero Believers        -0    0    e    -  0  1-9  d       d      lt   d  e-  0  1-9  d     0x 0-9a-f     i   Test This Regex  Hope I covered all number permutations that are supported in many programming languages  Good luck     Oh  forgot to mention  that those who want to validate a number includes a thousand separator  you should clean all the commas     first  as there may be any type of separator out there  you can t actually cover them all  But you can remove them first  before the number validation     JavaScript function clearSeparators number        return number replace    g            Similar post on my blog

User · Answer

Below is the perfect one for mentioned requirement      0-9  1 3    0-9  3            1  0-9

User · Answer

I ve tested all given regexes but unfortunately none of them pass those tests       String   goodNums   3   -3   0   0 0   1 0   0 1        String   badNums   001   -00 2    3   3    a          -    -1   --1   - 1   -0    2  3    2-    2   3    2 4 3    5-6-7      Here is the best I wrote that pass all those tests      - 0     d      -  1-9    d       d       0

User · Answer

Here is my regex for validating numbers     -  1-9    d       d        - 0     d  1-9      0    Valid numbers   String   validNumbers   3   -3   0   0 0   1 0   0 1   0 0001   -555   94549870965      Invalid numbers   String   invalidNumbers   a          -   001   -00 2   000 5    3   3     -1   --1   - 1   -0

User · Answer

0-9           matches any number with or without coma or dots  it can match           122          122 354          122 88          112 262 123 7678   bug  it also matches 262 4377 3883   but it doesn t matter parctically

User · Answer

Try this code  hope it will help you  String regex       d           d       for integer and decimal like 232 232 12

User · Answer

A simple regex to match a numeric input and optional 2 digits decimal     d        d 0 2       You can modify the  0 2  to match your decimal preference  min  max   Snippet for validation   x000D   x000D  const source   document getElementById  source    source addEventListener  input   allowOnlyNumberAndDecimals    function allowOnlyNumberAndDecimals e      let str   e target value   const regExp      d        d 0 2         status   regExp test str     valid     invalid     console log status           source value    x000D   lt input type  text  id  source    gt  x000D   x000D   x000D

[regex] Decimal or numeric values in regular expression validation

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