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Expression nodes transform data using the ZEN expression language. Use them to calculate values, reshape data, and prepare outputs.
Creating an expression node
Drag an Expression node onto the canvas
Connect it to your data flow
Click Edit Expression to open the editor
Define output fields and their expressions
Expression structure Each expression node produces an output object. You define fields and the expressions that calculate them:
Accessing data Reference input data using dot notation:
customer.name // Nested object access order.items[0].price // Array indexing
Referencing previous nodes Use $nodes to access output from any upstream node by its name:
$nodes.CreditCheck.rating // Output from "CreditCheck" node $nodes.RiskScore.value // Output from "RiskScore" node $nodes["My Node"].field // Use brackets for names with spaces
See Useful patterns for more examples.
Operators Arithmetic price * quantity // Multiplication total / count // Division base + bonus // Addition gross - deductions // Subtraction amount % 100 // Modulo (remainder) 2 ^ 10 // Power (1024)
Comparison age >= 18 // Greater than or equal status == "active" // Equal tier != "basic" // Not equal score < threshold // Less than
Logical isActive and hasPermission // Both must be true isAdmin or isOwner // Either can be true not isBlocked // Negation
Ternary (conditional) score > 70 ? "pass" : "fail" age >= 18 ? "adult" : age >= 13 ? "teen" : "child"
Null handling user.nickname ?? user.name ?? "Anonymous" // First non-null value
Range checks age in [18..65] // Inclusive range score in (0..100) // Exclusive range value not in [1..10] // Outside range
Built-in functions Math Function Example Result abs(n)abs(-5)5round(n)round(3.7)4floor(n)floor(3.9)3ceil(n)ceil(3.1)4min(arr)min([3, 1, 4])1max(arr)max([3, 1, 4])4sum(arr)sum([1, 2, 3])6avg(arr)avg([10, 20, 30])20
String Function Example Result len(s)len("hello")5upper(s)upper("hello")"HELLO"lower(s)lower("HELLO")"hello"trim(s)trim(" hi ")"hi"contains(s, sub)contains("hello", "ell")truestartsWith(s, prefix)startsWith("hello", "he")truesplit(s, delim)split("a,b,c", ",")["a","b","c"]
Array Function Example Result len(arr)len([1, 2, 3])3map(arr, expr)map([1, 2, 3], # * 2)[2, 4, 6]filter(arr, expr)filter([1, 2, 3, 4], # > 2)[3, 4]some(arr, expr)some([1, 2, 3], # > 2)trueall(arr, expr)all([1, 2, 3], # > 0)trueflatMap(arr, expr)flatMap([[1,2], [3]], #)[1,2,3]
The # symbol represents each element when iterating over arrays.
Date Function Example Result d(str)d("2024-01-15")Date object d().year()d("2024-01-15").year()2024d().month()d("2024-01-15").month()1d().day()d("2024-01-15").day()15d().add(n, unit)d("2024-01-15").add(7, "d")7 days later d().diff(d2, unit)d("2024-01-15").diff("2024-01-01", "day")14
Common patterns Calculate totals Categorize values Work with dates 