js regex replace multiple backreferences

Question

I am trying to replace a string based on all matched groups by regex. I cannot use the $1..$9 backreferences as the number of groups in the regex varies.

Here is a working example with 1 group:

string = 'ab ac';
regex = new RegExp( "(^|\\s)(a)", "ig" );
template = "$1<u>$2</u>";
replace = string.replace(regex, template);

But this logic doesn't work when there is more than 1 group:

string = 'ab bc';
regex = new RegExp( "(^|\\s)(a)|(^|\\s)(b)", "ig" );
template = "$1<u>$2</u>";
replace2 = string.replace(regex, template);

What should I use as 'template' to match all groups?

This jsfiddle may make it easier to understand: https://jsfiddle.net/wfo3n7rs/

Any reason you can't stick to using two capture groups, ala: "(^|\\s)(a|b)"? — James Thorpe
– James Thorpe, Commented Dec 29, 2015 at 16:29
@AvinashRaj Yeah, assuming it's only ever single characters like this that works too, and wouldn't for instance ever need to be (a|bc). — James Thorpe
– James Thorpe, Commented Dec 29, 2015 at 16:34
@gipadm: How simplified is your example? If the answer posted does not help you, you can make use of a callback function inside the replace method. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Dec 29, 2015 at 17:00

Federico Piazza · Accepted Answer · 2015-12-29 16:33:19Z

3

You can change your regex to:

regex = new RegExp( "(^|\\s)([ab])", "ig" );

Working demo

answered Dec 29, 2015 at 16:33

Federico Piazza

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