Bash -> jq CheatSheet

jq.bash

# Aggregate keys of all objects in an array
jsonArrayData | jq '[.[] | keys] | flatten | unique'

# Map array to reduced objects and sort by a field
# Assumes array of {id, name, items:[]}
jsonArrayData | jq '[.[] | {id, name, itemCount:.items | length}] | sort_by(.itemCount)'

# Filter an array by matching property
jsonArrayData | jq '. [] | select(.id == "SomeId")'

# Property contains
jsonArrayData | jq '.[] | select(.name | contains("some string"))'

# Cast string to upper or lowercase
jsonArrayData | jq '.[] | select(.name | ascii_downcase | contains("lowercase string"))'
jsonArrayData | jq '.[] | select(.name | ascii_upcase | contains("UPPERCASE STRING"))'

# Convert array to object keyed on array[].id
jsonArrayData | jq 'map({(.id|tostring): .}) | add' 
# Given this:
# [
#   {
#     "id": "Thing A",
#     "thing": "stuff"
#    },
#   {
#     "id": "Thing B",
#     "thing": "stuff"
#    }
# ]
#
# Yields this:
# {
#   "Thing A": {
#     "id": "Thing A",
#     "thing": "stuff"
#    },
#    "Thing B": {
#     "id": "Thing B",
#     "thing": "stuff"
#    }
# }

# Bring parent data into a flattened child array
# (Keep in mind that if parent and child have fields with the same name, parent fields may need to be mapped to unique names to avoid collision)
jsonArrayData | jq '[.[] | .childArray + del(.childArray)]'
# Given this:
# {
#     parentId:123,
#     children:[
#         {
#             name: "Child1"
#         },
#         {
#             name: "Child2"
#         }
#     ]
# }
#
# Yields this:
# [
#     {
#         parentId: 123,
#         name: "Child1"
#     },
#     {
#         parentId: 123,
#         name: "Child2"
#     }
# ]