Expressions

Expressions connect template content to data. Each expression is stored in all three supported languages, and the rendering engine evaluates the one matching the configured default.

Expression languages

Simple Path

Lightweight dot-path traversal for straightforward data access:

recipientName
address.city
items[0].description

Best for direct property lookups without transformation.

JSONata

The default expression language, using the Dashjoin implementation. Supports paths, filters, aggregations, and formatting:

$uppercase(recipientName)
$sum(items.amount)
$now('[D] [MNn] [Y]')
items[price > 100].description

JavaScript

GraalJS-sandboxed JavaScript for complex logic. No file system or network access is available:

data.items.filter(i => i.amount > 100).length
new Date(data.decisionDate).toLocaleDateString('nl-NL')

Where expressions are used

Text interpolation — {{expression}} within rich text blocks, rendered as inline chips
Conditional visibility — Determines whether a conditional block is shown or hidden
Loop iteration — Defines the array that a loop block iterates over
Table cell values — Binds data table columns to data paths

In the UI

The expression dialog lets authors write and test expressions. It provides:

Live evaluation preview — Shows the resolved value against the selected data example in real time
JSONata reference — Built-in documentation for JSONata syntax and functions
Language selector — Switch between Simple Path, JSONata, and JavaScript