JSONataの基本
JSONataの基本的なことは以下がわかりやすいです。
本題: JSONataオブジェクト操作チートシート
Node-REDのフローで役に立つJSONataによるオブジェクト操作のチートシートです（※Beforeの値がmsg.payloadを流れてきた前提）
1. オブジェクト内の特定のキー名を変更する
Before:
{
"name": "Alice",
"age": 30
}
JSONata:
{
"fullName": payload.name,
"age": payload.age
}
After:
{
"fullName": "Alice",
"age": 30
}
2. ネストされたオブジェクトをフラットにする
Before:
{
"name": "Bob",
"details": {
"age": 25,
"city": "New York"
}
}
JSONata:
{
"name": payload.name,
"age": payload.details.age,
"city": payload.details.city
}
After:
{
"name": "Bob",
"age": 25,
"city": "New York"
}
3. 2が配列の場合
Before:
[
{
"name": "Joe",
"details": {
"age": 18,
"city": "Texas City"
}
},
{
"name": "Charlie",
"details": {
"age": 22,
"city": "San Francisco"
}
},
{
"name": "Diana",
"details": {
"age": 28,
"city": "New York"
}
}
]
JSONata:
payload.{
"name": name,
"age": details.age,
"city": details.city
}
After:
[
{
"name": "Joe",
"age": 18,
"city": "Texas City"
},
{
"name": "Charlie",
"age": 22,
"city": "San Francisco"
},
{
"name": "Diana",
"age": 28,
"city": "New York"
}
]
4. 配列内のオブジェクトの特定のフィールドだけを抽出する
Before:
[
{
"name": "Joe",
"age": 18
},
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
}
]
JSONata:
payload.name
After:
["Joe", "Charlie", "Diana"]
5. 条件によるフィルタリング
Before:
[
{
"name": "Joe",
"age": 18
},
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
}
]
JSONata:
payload[age >= 21]
After:
[
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
}
]
6. 配列内のオブジェクトのキーを別の値に変換する
Before:
[
{ "oldKey": "value1" },
{ "oldKey": "value2" }
]
JSONata:
payload.{ "newKey": oldKey }
After:
[
{"newKey": "value1"},
{"newKey": "value2"}
]
7. 配列の要素を削除する（特定の値を持つ要素を除外）
Before:
[
{
"title": "task1",
"status": "completed"
},
{
"title": "task2",
"status": "pending"
},
{
"title": "task3",
"status": "progress"
}
]
JSONata:
payload[status != "completed"]
After:
[
{
"title": "task2",
"status":"pending"
},
{
"title":"task3",
"status":"progress"
}
]
8. 数値の集計（合計）
Before:
[
{ "price": 100 },
{ "price": 200 },
{ "price": 150 }
]
JSONata:
$sum(payload.price)
After:
450
9. デフォルト値を適用する（値が存在しない場合）
Before:
[
{
"name": "Joe",
"age": null
},
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
}
]
JSONata:
payload.{ "name": name, "age": age ? age : 18 }
After:
[
{
"name": "Joe",
"age": 18
},
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
}
]
10. オブジェクトから特定のキーを削除する
Before:
{
"user": {
"id": 12345,
"name": "Helen",
"password": "secret"
}
}
JSONata:
{
"id": payload.user.id,
"name": payload.user.name
}
After:
{
"id": 12345,
"name": "Helen"
}
11. 配列の長さを取得する
Before:
[
{ "name": "Joe", "age": 18 },
{ "name": "Charlie", "age": 22 },
{ "name": "Diana", "age": 28 }
]
JSONata:
$count(payload)
After:
3
12. 配列の特定の範囲を取得する
Before:
[
{ "name": "Joe", "age": 18 },
{ "name": "Charlie", "age": 22 },
{ "name": "Diana", "age": 28 },
{ "name": "Heima", "age": 38 }
]
JSONata:
payload[[1..3]]
After:
[
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
},
{
"name": "Heima",
"age": 38
}
]
13. 配列の要素をソートする
Before:
[
{ "name": "Joe", "age": 18 },
{ "name": "Charlie", "age": 22 },
{ "name": "Diana", "age": 28 }
]
JSONata:
payload^(-age)
After:
[
{
"name": "Diana",
"age": 28
},
{
"name": "Charlie",
"age": 22
},
{
"name": "Joe",
"age": 18
}
]
14. 条件に基づいた値の変換
Before:
[
{ "name": "Joe", "age": 18 },
{ "name": "Charlie", "age": 22 },
{ "name": "Diana", "age": 28 }
]
JSONata:
payload.{ "name": name, "category": age >= 21 ? "adult" : "minor" }
After:
[
{ "name": "Joe", "category": "minor" },
{ "name": "Charlie", "category": "adult" },
{ "name": "Diana", "category": "adult" }
]
15. 重複する要素の削除
Before:
[
{ "name": "Joe", "age": 18 },
{ "name": "Charlie", "age": 22 },
{ "name": "Joe", "age": 18 }
]
JSONata:
$distinct(payload)
After:
[
{ "name": "Joe", "age": 18 },
{ "name": "Charlie", "age": 22 }
]
16. 部分一致によるフィルタリング
Before:
[
{ "title": "Node-RED tutorial" },
{ "title": "JSONata guide" },
{ "title": "JavaScript basics" }
]
JSONata:
payload[title ~> /.*tutorial.*/]
After:
[
{ "title": "Node-RED tutorial" }
]
17. 特定の値をキーとして新しいオブジェクトを作る
Before:
[
{
"name": "Joe",
"age": 18
},
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
}
]
JSONata:
payload.{ $lookup("name"): $ }
After:
[
{
"Joe": {
"name": "Joe",
"age": 18
}
},
{
"Charlie": {
"name": "Charlie",
"age": 22
}
},
{
"Diana": {
"name": "Diana",
"age": 28
}
}
]
18. 17の逆
Before:
[
{
"Joe": {
"name": "Joe",
"age": 18
}
},
{
"Charlie": {
"name": "Charlie",
"age": 22
}
},
{
"Diana": {
"name": "Diana",
"age": 28
}
}
]
JSONata:
payload.*
After:
[
{
"name": "Joe",
"age": 18
},
{
"name": "Charlie",
"age": 22
},
{
"name": "Diana",
"age": 28
}
]
19. 17の逆で且つネストをフラットにする
Before:
[
{
"Joe": {
"name": "Joe",
"details": {
"age": 18,
"city": "Texas City"
}
}
},
{
"Charlie": {
"name": "Charlie",
"details": {
"age": 22,
"city": "San Francisco"
}
}
},
{
"Diana": {
"name": "Diana",
"details": {
"age": 28,
"city": "New York"
}
}
}
]
JSONata:
payload.{
"name": $lookup($, $keys())[0].name,
"age": $lookup($, $keys())[0].details.age,
"city": $lookup($, $keys())[0].details.city
}
After:
[
{
"name": "Joe",
"age": 18,
"city": "Texas City"
},
{
"name": "Charlie",
"age": 22,
"city": "San Francisco"
},
{
"name": "Diana",
"age": 28,
"city": "New York"
}
]