JQ substitute values in one array based on values from different array

Question

I would like in JQ to substitute the values in the first array with the names in the second array based on the key "size" while keeping the length of the first array unchanged.

[
    [{\"size\":0},{\"size\":1},{\"size\":2},{\"size\":3},{\"size\":4},{\"size\":5},{\"size\":6},{\"size\":7},{\"size\":8},{\"size\":9},{\"size\":0},{\"size\":1},{\"size\":2},{\"size\":3},{\"size\":4},{\"size\":5},{\"size\":6},{\"size\":7},{\"size\":8},{\"size\":0},{\"size\":1},{\"size\":2},{\"size\":3},{\"size\":4},{\"size\":5},{\"size\":6},{\"size\":7},{\"size\":8}]
    
    [{\"size\":0,\"name\":\"6M\"},{\"size\":1,\"name\":\"6.5M\"},{\"size\":2,\"name\":\"7M\"},{\"size\":3,\"name\":\"7.5M\"},{\"size\":4,\"name\":\"8M\"},{\"size\":5,\"name\":\"8.5M\"},{\"size\":6,\"name\":\"9M\"},{\"size\":7,\"name\":\"9.5M\"},{\"size\":8,\"name\":\"10M\"},{\"size\":9,\"name\":\"11M\"}]
]

So the wanted result would look like this:

[{\"size\":6M},{\"size\":6.5M},{\"size\":7M},{\"size\":7.5M},{\"size\":8M},{\"size\":8.5M},{\"size\":9M},{\"size\":9.5M},{\"size\":10M},{\"size\":11M},{\"size\":6M},{\"size\":6.5M},{\"size\":7M},{\"size\":7.5M},{\"size\":8M},{\"size\":8.5M},{\"size\":9M},{\"size\":9.5M},{\"size\":10M},{\"size\":6M},{\"size\":6.5M},{\"size\":7M},{\"size\":7.5M},{\"size\":8M},{\"size\":8.5M},{\"size\":9M},{\"size\":9.5M},{\"size\":10M}]

I used this input to obtain the above arrays jq "[.DATA.product.traits|([.colors.colorMap[]| {size:.sizes[]}]), ( [.sizes.sizeMap[]| {size:.id, name}])]" and then tried using if-then-else statement ( |if (.[0:-1][][].size ==.[-1][].size) then [.[-1][].name ] else null end" ) but I was unable to reach the desired output..

Answer 1

Given the input

[
  [
    {"size":0}, {"size":1}, {"size":2}, {"size":3}, {"size":4},
    {"size":5}, {"size":6}, {"size":7}, {"size":8}, {"size":9},
    {"size":0}, {"size":1}, {"size":2}, {"size":3}, {"size":4},
    {"size":5}, {"size":6}, {"size":7}, {"size":8}, {"size":0},
    {"size":1}, {"size":2}, {"size":3}, {"size":4}, {"size":5},
    {"size":6}, {"size":7}, {"size":8}
  ],
  [
    {"size":0,"name":"6M"}, {"size":1,"name":"6.5M"},
    {"size":2,"name":"7M"}, {"size":3,"name":"7.5M"},
    {"size":4,"name":"8M"}, {"size":5,"name":"8.5M"},
    {"size":6,"name":"9M"}, {"size":7,"name":"9.5M"},
    {"size":8,"name":"10M"}, {"size":9,"name":"11M"}
  ]
]

you can generate an INDEX over the second item, and use it for reference in a map on the first

(.[1] | INDEX(.size)) as $map | .[0] | map($map[.size | tostring])

to get

[
  {"size":0,"name":"6M"}, {"size":1,"name":"6.5M"},
  {"size":2,"name":"7M"}, {"size":3,"name":"7.5M"},
  {"size":4,"name":"8M"}, {"size":5,"name":"8.5M"},
  {"size":6,"name":"9M"}, {"size":7,"name":"9.5M"},
  {"size":8,"name":"10M"}, {"size":9,"name":"11M"},
  {"size":0,"name":"6M"}, {"size":1,"name":"6.5M"},
  {"size":2,"name":"7M"}, {"size":3,"name":"7.5M"},
  {"size":4,"name":"8M"}, {"size":5,"name":"8.5M"},
  {"size":6,"name":"9M"}, {"size":7,"name":"9.5M"},
  {"size":8,"name":"10M"}, {"size":0,"name":"6M"},
  {"size":1,"name":"6.5M"}, {"size":2,"name":"7M"},
  {"size":3,"name":"7.5M"}, {"size":4,"name":"8M"},
  {"size":5,"name":"8.5M"}, {"size":6,"name":"9M"},
  {"size":7,"name":"9.5M"}, {"size":8,"name":"10M"}
]

Demo