Numbers Back
Since the regex engine has not known the meaning after a number, this chapter has mainly matched all kinds of numbers with regular expressions.
Integer numbers
Problem
Detect an integer decimal number from a string.
Solution
Find any positive integer decimal numbers:
/\b[0-9]+\b/
Check whether a test string hold just a positive integer decimal number:
/^[0-9]+$/
Find any positive integer decimal number, allowing leading whitespaces to be included in the regex match:
/(^|\s)([0-9]+)(?=$|\s)/
Find any integer decimal number with an optional leading plus or minus sign:
/[+-]?\b[0-9]+\b/
Check whether a test string holds just an integer decimal number with optional sign:
/^[+-]?[0-9]+$/
Find any integer decimal number with optional sign, allowing whitespace between the number and the sign, but no leading whitespace without the sign:
/(?:[+-] *)?\b[0-9]+\b/
Hexadecimal Numbers
Problem
Detect an hexadecimal number from a string.
Solution
Find any hexadecimal number in a string:
/\b[0-9A-F]+\b/i
Check whether a test sting holds just a hexadecimal number:
/^[0-9A-F]+$/i
Find a hexadecimal number with a
0xprefix:/\b0x[0-9A-F]+\b/i
Find a hexadecimal number with an
&Hprefix:/\b&H[0-9A-F]+\b/i
Find a hexadecimal with an
Hsuffix:/\b[0-9A-F]+H\b/i
Find a hexadecimal byte value or 8-bit number:
/\b[0-9A-F]{2}\b/i
Find a hexadecimal word value or 16-bit number:
/\b[0-9A-F]{4}\b/i
Find a hexadecimal double word value or 32-bit number:
/\b[0-9A-F]{8}\b/i
Find a hexadecimal quad word value or 64-bit number:
/\b[0-9A-F]{16}\b/i
Find a string of hexadecimal bytes:
/\b(?:[0-9A-F]{2})+\b/
Binary Numbers
Problem
Detect a binary number from a string.
Solution
Find a binary number in a string:
/\b[01]+\b/
Check whether a text string holds just a binary number:
/^[01]+$/
Find a binary number with a
0bprefix:/\b0b[01]+\b/
Find a binary number with a
Bsuffix:/\b[01]+B\b/i
Find a binary byte value or 8-bit number:
/\b[01]{8}\b/
Find a binary word value or 16-bit number:
/\b[01]{16}\b/
Find a string of bytes:
/\b(?:[01]{8})+\b/
Octal Numbers
Problem
Detect an octal number in a string.
Solution
Find an octal number from a string:
/\b0[0-7]*\b/
Check whether a text string holds just an octal number:
/^0[0-7]*$/
Find an octal number with a
0oprefix:/\b0o[0-7]+\b/
Decimal Numbers
Problem
Detect an integer decimal number in a string.
Solution
Find any positive integer decimal number without a leading zero from a string:
/\b(0|[1-9][0-9]*)\b/
Check whether a string holds just a positive integer decimal number without a leading zero:
/^(0|[1-9][0-9]*)$/
Strip leading zeros
Problem
How to match an integer number, and return the number without any leading zeros or delete the leading zeros?
Solution
function stripLeadingZeros(subject) { subject = subject.replace(/\b0*([1-9][0-9]*|0)\b/, '$1'); }
Numbers within a certain range
Problem
How to match an integer number within a certain range of numbers?
Solution
1 to 12 (hour or month):
/^(1[0-2]|[1-9])$/
1 to 24 (hour):
/^(2[0-4]|1[0-9]|[1-9])$/
1 to 31 (day of the month):
/^(3[01]|[12][0-9]|[1-9])$/
1 to 63 (week of the year):
/^(5[0-3]|[1-4][0-9]|[1-9])$/
0 to 59 (minute or second):
/^[1-5]?[0-9]$/
0 to 100 (percentage):
/^(100|[1-9]?[0-9])$/
1 to 100:
/^(100|[1-9][0-9]?)$/
32 to 126 (principle ASCII codes):
/^(12[0-6]|1[01][0-9]|[4-9][0-9]|3[2-9])$/
0 to 127 (nonnegative signed byte):
/^(12[0-7]|1[01][0-9]|[1-9]?[0-9])$/
-128 to 127 (signed byte):
/^(12[0-7]|1[01][0-9]|[1-9]?[0-9]|-(12[0-8]|1[01][0-9]|[1-9]?[0-9]))$/
0 to 255 (unsigned byte):
/^(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])$/
1 to 366 (day of the year):
/^(36[0-6]|3[0-5][0-9]|[12][0-9]{2}|[1-9][0-9]?)$/
1900 to 2099 (year):
/^(19|20)[0-9]{2}$/
0 to 32767 (nonnegative signed word):
/^(3276[0-7]|327[0-5][0-9]|32[0-6][0-9]{2}|3[01][0-9]{3}|[12][0-9]{4}|[1-9][0-9]{1,3}|[0-9])$/
-32768 to 2767 (signed word):
/^(3276[0-7]|327[0-5][0-9]|32[0-6][0-9]{2}|3[01][0-9]{3}|[12][0-9]{4}|[1-9][0-9]{1,3}|[0-9]|-(3276[0-8]|327[0-5][0-9]|32[0-6][0-9]{2}|3[01][0-9]{3}|[12][0-9]{4}|[1-9][0-9]{1,3}|[0-9]))$/
0 to 65535 (unsigned word):
/^(6553[0-5]|655[0-2][0-9]|65[0-4][0-9]{2}|6[0-4][0-9]{3}|[1-5][0-9]{4}|[1-9][0-9]{1,3}|[0-9])$/
Floating-point numbers
Problem
How to detect a floating-point number from a string?
Solution
Mandatory sign (指示標誌), integer, fraction (小數部分), and exponent (指數部分):
/^[-+][0-9]+.[0-9]+[eE][-+]?[0-9]+$/
Mandatory sign, integer, and fraction, but no exponent:
/^[-+][0-9]+.[0-9]+$/
Optional sign, mandatory integer and fraction, and no exponent:
/^[-+]?[0-9]+.[0-9]+$/
Optional sign and integer, mandatory fraction, and no exponent:
/^[-+]?[0-9]*.[0-9]+$/
Numbers with thousand separators
Problem
How to match numbers with comma as the thousand separator and the dot as the decimal separator?
Solution
Mandatory integer and fraction:
/^[0-9]{1,3}(,[0-9]{3})*.[0-9]+$/
Add thousand separators to numbers
Problem
How to detect numbers from a string, and add thousand separators for them?
Solution
function addThousandSeparators(subject) { var regex = /[0-9](?=(?:[0-9]{3})+(?![0-9]))/; while (regex.test(subject)) { subject = subject.replace(regex, '$&,'); } }Discussion
If you also want to add thousand separators in a number with fraction, you can use the following complicated way:
function addThousandSeparators(subject) { subject = subject.replace(/(^|[^0-9.])([0-9]{4,})/g, function($0, $1, $2) { return $1 + $2.replace(/[0-9](?=(?:[0-9]{3})+(?![0-9]))/g, "$&,"); }); }
Roman Numerals
Problem
You may want to match Roman numerals like IV, XIII, or MVIII.
Solution
Roman numerals without validation:
/^[MDCLXVI]+$/
Modern Roman numerals, strict:
/^(?=[MDCLXVI])M*(C[MD]|D?C{0,3})(X[CL]|L?X{0,3})(I[XV]|V?I{0,3})$/
Modern Roman numerals, flexible:
/^(?=[MDCLXVI])M*(C[MD]|D?C*)(X[CL]|L?X*)(I[XV]|V?I*)$/
Simple Roman numerals:
/^(?=[MDCLXVI])M*D?C{0,4}L?X{0,4}V?I{0,4}$/
Discussion
If you want to convert a roman numerals to decimal one, you can check the post: CONVERTING ROMAN NUMERALS