Expressions and code
Built-in methods and variables in Duaer expressions
Duaer expressions provide variables for reading data and methods you call on a value. The Code node runs plain JavaScript and native Luxon. A method that is a Duaer extension may be missing there, or take different arguments.
Expressions and the Code node are not the same engine
The Duaer expression editor can use $json, $("Node name"), $now, $if(), and transformation methods on strings, arrays, and dates. The Code node does not use that expression engine.
If the Code node says is not a function, check whether the method exists only in expressions. Date formatting can use format() in an expression. In the Code node, use Luxon’s toFormat(). plus() and minus() accept (amount, unit) in an expression. In the Code node they expect an object such as { days: 7 }. The expression-style call may not throw in the Code node, and still not do what you meant.
$if(), $ifEmpty(), and $jmespath() exist only in expressions. The lookup is Methods and variables reference.
Which page to open
- The current item, earlier nodes, conditions, and empty values: Convenience methods in Duaer expressions.
- Arrays, booleans, dates, numbers, objects, and strings: Data transformation methods by type.
- HTTP node pagination: Variables for HTTP node pagination.
- JSON queries: Query JSON with JMESPath.
Questions
Can Duaer transformation methods run in the Code node?
Duaer transformation methods, $if(), and $jmespath() belong to expressions. The Code node runs plain JavaScript and native Luxon. format() in an expression becomes toFormat() in the Code node. plus(7, "days") in the Code node is plus({ days: 7 }).
Which variable reads the current item in a Duaer expression?
In a Duaer expression, the current item is $json and the current item’s file is $binary. An earlier node is $("Node name").item, first(), last(), or all().
In this section
Define reusable variables in Duaer
Duaer variables store a value for more than one digital organization. Expressions and the Code node read them as $vars.key. Every variable is a string, and a run only reads it.
ExpressionsWrite expressions in Duaer
A Duaer expression sits inside {{ }} and reads the current item, earlier nodes, and variables from a node parameter. When you are only reshaping fields, prepare them in an Edit Fields (Set) node first.
ExpressionsConvenience methods in Duaer expressions
Duaer expressions use $json for the current item, $("Node name") for an earlier node, and $now and $if() for time and conditions. These names are available in expression mode on a parameter.
ExpressionsVariables for HTTP node pagination
The Duaer HTTP Request node provides $pageCount, $request, and $response in pagination expressions. Those three names work only in that node. Other nodes cannot read them.
TransformData transformation methods by type
Duaer expressions call transformation methods on a value, such as {{ $json.name.toTitleCase() }}. The methods are grouped by array, boolean, date, number, object, and string. The Code node does not have these extensions.
TransformArray transformation methods
In a Duaer expression, call an array method on the array, such as {{ $json.ids.unique() }}. average, max, and min throw if any element is not a number.
TransformBoolean transformation methods
In a Duaer expression, a boolean can be tested for empty and converted to a number or a string. true becomes 1 as a number. false becomes 0.
TransformDate transformation methods
In a Duaer expression, $now and $today are Luxon DateTime values. Call toDateTime() on a string or number before format, plus, or setZone.
TransformNumber transformation methods
In a Duaer expression, number methods round, test even or odd, and convert to a boolean, a string, or a DateTime. round goes to the nearest number. ceil goes up. floor goes down.
TransformObject transformation methods
In a Duaer expression, object methods test fields, drop fields, merge objects, and encode an object as a query string. keys() and values() return the field names and the values.
TransformString transformation methods
In a Duaer expression, string methods change case, slice text, test emails and URLs, and encode or decode base64 and URLs. Call the method on the string.
QueryQuery JSON with JMESPath
Duaer queries JSON with $jmespath(object, "query"). Expressions and the JavaScript Code node can call it. The Python Code node does not have this function.
DatesUse Luxon for dates in expressions
Dates in a Duaer expression are Luxon DateTime values. $now and $today are DateTime values already. The Code node uses native Luxon. format() and plus(amount, unit) do not carry over unchanged.
ExamplesDuaer expression examples
These examples run in Duaer expression mode. They read the current item, fill a default, format a date, and move a large reshape into Edit Fields (Set).
ExamplesMethods and variables reference
These are the names used most often in a Duaer expression. The current item is $json, an earlier node is $("Node name"), variables are $vars, and transformation methods are grouped by data type.