CODEWITHSUNDEEP
javascriptregex
Milor123
Milor123

Reputation: 555

Javascript Regex, re use a group to mach another group

Hi guys I want re use the expression for capture other group

For example:

I need search US $4.5-8.8
The structure is: Part1-Part2

The part1 and the part2 have the same code, I could use the part1 like group, and then re use in the part2

I've doned the expression until 4.5-XXXX

US \$([0-9]{1}(?=\.{1})\.{1}[0-9]+)(?=\-)\-

check in: https://regex101.com/r/E2MjWh/1

What should I do for re use the first group? It is easy in other lenguague, but I can't do it in javascript..

PD: I need it in regex, not include javascript code like var... etc etc..

Upvotes: 1

Views: 51

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626794

First, have a look at your regex: the positive lookaheads are not really necessary there as they just require the same as the following consuming subpatterns. (?=\.{1})\.{1} means *require 1 dot immediately to the right of the current location and then match the dot, and (?=\-)\- has a similar meaning requiring and matching a - symbol.

Now, you ask if you can repeat the same part of a pattern using just the regex syntax. No, it is not possible in JS regex.

You may use the following regex to match the whole string like yours:

/US\s+\$(\d+\.\d+)-(\d+\.\d+)/

See the regex demo. Sure, you may add word boundaries (to match US as a whole word) or anchors (to match the whole input string) or replace the \d+\.\d+ part with \d*\.?\d+ (to match both integers or floats) to further enhance the pattern.

There is a way to shorten the pattern by placing the repetitive part into a variable and build the regex dynamically using the constructor notation:

var price = "\\d*\\.?\\d+";
var reg = new RegExp("US\\s+\\$(" + price + ")-(" + price + ")");

Add the required modifiers if necessary.

Upvotes: 1

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