CODEWITHSUNDEEP
javascriptregexreplace
TonyW
TonyW

Reputation: 18875

Creating a regex pattern with a variable for replacing a dot

I need to replace the decimal separator in a string, and the decimal separators could be a dot . (e.g. English) or a comma , (e.g. German). So I have the variable sep for containing the separator string.

To convert the English-based decimal separator, I do the following replacement, but I got ,dd,dd rather than 120,dd:

var sep = '.';
var numberStr = '120.31';
numberStr = numberStr.replace(new RegExp(sep + '\\d{2}', 'g'), ',dd');
console.log(numberStr);

Does anyone know where I went wrong?

Upvotes: 1

Views: 293

Answers (2)

basst314
basst314

Reputation: 184

The dot-character in RegularExpressions matches one single character, regardless of the actual character itself (details depending on the programming language / regex engine / flags in use).

If you want to match a dot, your separator should escape the regex dot-selector character like var sep = '\\.'; to match an actual dot, not 'any single character'.

So your error occurs because in 120.31 the pattern [any character followed by 2 numbers] is found/replaced twice, once for 120 and once for .31, as 1 aswell as . match the regex dot-selector '.'.

For details see the Regex Cheat Sheet

Upvotes: 4

raina77ow
raina77ow

Reputation: 106385

You need to escape the separator (so that it'll be treated by RegExp engine as is) by prefixing it with \ character:

var escapedSep = sep.replace(/[.?*+^$[\]\\(){}|-]/g, "\\$&");
numberStr = numberStr.replace(new RegExp(escapedSep + '\\d{2}', 'g'), ',dd');

Otherwise . is treated as a RegExp metacharacter, matching on any symbol (except line breaks).

Upvotes: 1

Related Questions