Expressions and code
Methods 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.
Reading data
- $json.field is a field on the current item.
- $binary is the file on the current item.
- $("Node name").item, .first(), .last(), and .all() are the linked item, the first item, the last item, or every item from that node.
- $itemIndex and $runIndex are this item’s position and how many times this node has run. Both start at 0.
- $vars.key reads Define reusable variables in Duaer.
- $execution.id and $workflow.name are this execution and this digital organization.
- $pageCount, $request, and $response exist only in HTTP Request pagination. See Variables for HTTP node pagination.
Conditions and transformations
- $if(condition, a, b) and $ifEmpty(value, default) choose a value or fill a default.
- $now, $today, and toDateTime() are dates. See Use Luxon for dates in expressions.
- $jmespath(object, "query") is in Query JSON with JMESPath.
- Methods for strings, arrays, numbers, objects, booleans, and dates are in Data transformation methods by type.
Questions
What reads the current item and an earlier node 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(). A reusable variable is $vars.key.
Is $pageCount a general Duaer variable?
No. In Duaer, $pageCount, $request, and $response exist only in pagination expressions on the HTTP Request node. Other nodes still read the current item with $json.
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.
ExpressionsBuilt-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.
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).