Nebula Shift Tab

JSONata Expressions

JSONata Basics Tutorial

JSONata is a lightweight query and transformation language designed specifically for JSON data.

1. Basic Syntax

Accessing Fields

name          // Access the 'name' field of the current object
user.name     // Access a nested field

Array Operations

items[0]              // Access the first element
items[name = "Alice"] // Filter the array
items.name            // Extract the 'name' field from all elements (automatic mapping)

2. Common Operators

Type Example Description
Comparison price > 100 Greater than
Logical active and price < 50 Logical AND
String "Hello " & name Concatenation
Arithmetic quantity * price Multiplication
Conditional status = "ok" ? "Yes" : "No" Ternary expression

3. Built-in Functions

$length(name)                         // String length
$substring(name, 0, 3)                // Extract substring
$join(names, ", ")                    // Join array into a string
$sum(prices)                          // Summation
$average(scores)                      // Average
$count(items)                         // Count
$sort(items, function($v){$v.price})  // Sort

4. Variables and Context

  • $ represents the current context.
  • Custom variables: $myVar := expression; $myVar * 2
  • Variables passed from the environment can be used directly in expressions (e.g., msg.payload in Node-RED).

5. Nebula Shift Tab Extension Functions

To facilitate usage, Nebula Shift Tab provides several additional functions to simplify operations in specific scenarios.

$array_rand(items)      // Randomly return an element from an array
$json_decode(item)      // Parse a JSON string into an object
$rand(min, max)         // Generate a random integer

6. Demo

Input:

{
  "order": {
    "id": "123",
    "items": [
      { "name": "Apple", "price": 1.2, "qty": 3 },
      { "name": "Banana", "price": 0.8, "qty": 5 }
    ]
  }
}

JSONata Expression:

$array_rand($.order.items).name

Output Result: Apple or Banana

7. Learning Resources

You can learn the complete JSONata syntax in the official documentation.

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