How can a string value be transformed and cast to number using jq

Question

Just trying to figure out how can this simple JSON fragment

[{ "rooms": "2 Rooms" }, { "rooms": "3 Rooms" }]

be transformed to

[{ "rooms": 2 }, { "rooms": 3 }]

I found in the documentations the reference to functions supporting regexp, but I cannot write more than this

[.[] | { "rooms": .rooms } ]

Answer 1

Here's one way that can easily be adapted to different requirements:

def extractNumber: gsub("[^0-9]";"") | tonumber;

map( map_values(extractNumber) )

A generalization

def extractNumber:
  . as $in 
  | gsub("[^0-9]";"")
  | if length == 0 then $in else tonumber end;

walk(if type == "object" then map_values(extractNumber) else . end)