JSONata¶

When a state machine (or a state) sets "QueryLanguage": "JSONata", field values may contain JSONata expressions. Stegflow evaluates them with the Jsonata.Net.Native library, a .NET port of JSONata.

This page covers the basics of what you can write. For the full expression and function language, use the upstream references:

• JSONata documentation
• JSONata function library (string, numeric, aggregation, boolean, array, object, date/time and higher-order functions)
• Jsonata.Net.Native for anything specific to the .NET port

Writing an expression¶

A JSONata expression is wrapped in {% %}. Anywhere a field takes a value, you can compute it:

{
  "QueryLanguage": "JSONata",
  "StartAt": "Greet",
  "States": {
    "Greet": {
      "Type": "Pass",
      "Output": "{% 'Hello, ' & $states.input.name %}",
      "End": true
    }
  }
}

A string without the {% %} markers is treated as a literal, not evaluated.

The $states context¶

Inside an expression, the reserved $states object exposes the runtime data:

Variables¶

Values set with Assign become variables, referenced with a leading $:

{
  "Type": "Pass",
  "Assign": { "total": "{% $states.input.a + $states.input.b %}" },
  "Next": "UseIt"
}

Later states read it as {% $total %}.

What you can use¶

Everything the JSONata language offers is available: path navigation, arithmetic and comparison operators, string and array manipulation, conditional (? :) and block expressions, and the full built-in function library ($sum, $map, $filter, $substring, $now, and so on). Refer to the JSONata function library for the complete list.