A pure Dart implementation of JSONata - the JSON query and transformation language.
import'package:jsonata_dart/jsonata_dart.dart';
voidmain() {
final data = {
'Account': {
'Name':'Firefly',
'Order': [
{'Product':'Hat', 'Price':9.99},
{'Product':'Shoes', 'Price':49.99},
]
}
};
// Path expressionsprint(Jsonata('Account.Name').evaluate(data)); // "Firefly"// Aggregationsprint(Jsonata(r'$sum(Account.Order.Price)').evaluate(data)); // 59.98// Transformationsprint(Jsonata('Account.Order.Product').evaluate(data)); // ["Hat", "Shoes"]// Custom functionsfinal expr =Jsonata(r'$double(value)');
expr.registerFunction(r'$double', (args, input, env) => (args[0] asnum) *2);
print(expr.evaluate({'value':21})); // 42// Variable bindingfinal expr2 =Jsonata(r'price * $tax');
expr2.bind(r'$tax', 1.1);
print(expr2.evaluate({'price':100})); // 110.0// Regular expressionsprint(Jsonata(r'$match("hello world", /\w+/)').evaluate({}));
// {"match": "hello", "index": 0, "groups": []}// Date/time functionsprint(Jsonata(r'$now()').evaluate({})); // Current ISO 8601 timestampprint(Jsonata(r'$fromMillis(1527152400000, "[D] [MNn] [Y]")').evaluate({})); // "24 May 2018"print(Jsonata(r'$toMillis("2018-05-24", "[Y]-[M01]-[D01]")').evaluate({})); // 1527120000000// Transform operator (function chaining)print(Jsonata(r'"hello" ~> $uppercase ~> $length').evaluate({})); // 5// Parent operator (access parent context)print(Jsonata(r'Account.Order.Product{`Product Name`: %.OrderID}').evaluate(data));
// Groups products by name with their parent order ID// Sort operatorprint(Jsonata(r'Account.Order.Price^($)').evaluate(data)); // [9.99, 49.99]// Focus operator (bind current item to variable)print(Jsonata(r'Account.Order@$o.Product.{ "product": Product, "orderId": $o.OrderID }').evaluate(data));
// Index bind operator (bind iteration index)print(Jsonata(r'Account.Order#$i.{ "index": $i, "product": Product }').evaluate(data));
}- Path expressions - Navigate JSON structures with dot notation
- Predicates and filters - Filter arrays with
[condition] - Wildcards -
*and**for matching - String functions -
$string,$length,$substring,$substringBefore,$substringAfter,$uppercase,$lowercase,$trim,$pad,$contains,$split,$join,$replace,$match,$base64encode,$base64decode - Numeric functions -
$number,$abs,$floor,$ceil,$round,$power,$sqrt,$random,$formatNumber,$formatBase,$formatInteger,$parseInteger - Aggregation functions -
$sum,$max,$min,$average,$count - Boolean functions -
$boolean,$not,$exists - Array functions -
$append,$count,$sort,$reverse,$shuffle,$distinct,$zip - Object functions -
$keys,$values,$spread,$merge,$each,$sift,$type,$lookup - Higher-order functions -
$map,$filter,$reduce,$sift,$each,$single - Regular expression functions -
$match,$replacewith regex,$containswith regex,$splitwith regex - Date/time functions -
$now,$millis,$fromMillis,$toMilliswith full XPath/XQuery picture string support - Transform operator -
~>for function chaining - Conditional expressions - Ternary
? :operator - Lambda expressions -
function($x) { $x * 2 } - Variable binding -
$variable := value - Partial application - Using
?placeholder - Custom functions - Register your own functions
- Parent operator -
%for accessing parent context in path expressions - Sort operator -
^(expr)for sorting arrays - Focus operator -
@$varfor binding current item to a variable - Index bind operator -
#$varfor binding iteration index to a variable
- Async expressions
This is a clean-room Dart implementation, not a transpilation. Key differences:
| Aspect | JavaScript | Dart |
|---|---|---|
| Undefined | Returns undefined | Returns null (internally uses sentinel) |
| Exceptions | Throws with code, message | Throws JsonataException with same codes |
| Custom functions | expr.registerFunction(name, fn, signature) | expr.registerFunction(name, fn) (no signature validation) |
| Async | Supports async expressions | Synchronous only |
Compiles a JSONata expression.
Evaluates the expression against JSON data. Returns the result or null if undefined.
Registers a custom function. The function receives (List<dynamic> args, dynamic input, Environment env).
Binds a variable for use in the expression.
Returns the parsed AST for inspection.
try {
Jsonata('invalid[').evaluate({});
} onJsonataExceptioncatch (e) {
print('${e.code}: ${e.message}'); // S0302: Expected ']'
}Error codes follow the JSONata specification.
MIT - see LICENSE