I'm trying to write a regex to capture any measurement unit in a string, considering that the unit can be before or after the number.

What I came up for the moment are two regex.

/\d*\.?,?\d \s?(kg|g|l)/gi that matches with

ABC 200g
EFG 5,4 Kg
HIL 2x20l

And (kg|g|l)\s?\d ,?\.?d* that matches with:

ABC g200
EFG kg 5,4
HIL l 20x2

How can I join the two regex to match with both:

ABC g200
EFG 5,4 Kg

CodePudding user response：

With a case insensitive pattern, match an optional k and g or l and an alternation | to match the pattern the other way as well.

The optional dot and comma can be in a character class [.,]? or else .?,? can also match both like .,

The word boundaries \b prevent a partial match after the unit.

\d*[.,]?\d \s*(?:k?g|l)\b|\b(?:k?g|l)\s*\d*[.,]?\d 

Regex demo

CodePudding user response：

With your shown samples, please try following regex.

(?:(?:(?:\d )g|(?:g\d ))|(?:(?:l\s*\d )|(?:\d \s*l))|(?:(?:\d ,\d \s*Kg)|(?:kg\s*\d ,\d )))

Online demo for above regex

Explanation: Adding detailed explanation for above.

(?:                                     ##Starting 1st capturing group from here.
  (?:                                   ##Starting 2nd capturing group from here.
     (?:\d )g|(?:g\d )                  ##Matching either digits followed by g OR g followed by digits(both conditions in non-capturing groups here).
  )                                     ##Closing 2nd capturing group here.
  |                                     ##Putting OR condition here.
  (?:                                   ##Starting 3rd capturing group here.
     (?:l\s*\d )|(?:\d \s*l)            ##Matching eiter l followed by 0 or more spaces followed by digits OR digits followed by 0 or more spaces followed by l.
  )                                     ##Closing 3rd capturing group here.
  |                                     ##Putting OR condition here.
  (?:                                   ##Starting 4th capturing group here.
     (?:\d ,\d \s*Kg)|(?:kg\s*\d ,\d )  ##Checking either digits followed by comma digits spaces Kg OR kg spaces digits comma digits here.
  )                                     ##Closing 4th capturing group here.
)                                       ##Closing 1st capturing group here.