How Does n8n Evaluate Dynamic Expressions in TypeScript Node Definitions?

When you see code like:

TYPESCRIPTCopied
outputs: `={{(${configuredOutputs})($parameter)}}`,

it's not that TypeScript itself supports some new templating engine—instead, it's leveraging n8n’s custom expression evaluation system.

How It Works

• Expression Wrapping: In n8n, strings wrapped with ={{ … }} are treated as expressions. At runtime, n8n detects these patterns in node parameter definitions and evaluates the content inside the curly braces.

• Function Injection: In this instance, configuredOutputs is a function that has been defined elsewhere in the node code. By writing (${configuredOutputs})($parameter), the code is essentially inserting the function into the expression and immediately calling it with $parameter as its argument.

• Dynamic Configuration: This design allows the node to dynamically calculate or transform configuration values at runtime using JavaScript logic. It’s a powerful way to let users or the node implementation itself decide which output route to take based on the evaluated result.

No Separate Template Engine

There isn’t a separate template engine that you need to set up or include from outside—the expression syntax (={{…}}) is built into the n8n runtime. This means that while the node source is written in TypeScript, the expressions within configuration objects are parsed by n8n’s engine when the workflow runs.

In Summary

• The ={{…}} syntax tells n8n, "Hey, evaluate this as an expression."
• Inside that expression, configuredOutputs is a function reference that gets invoked with $parameter.
• This mechanism isn’t a feature of TypeScript itself but part of how n8n handles dynamic node configurations at runtime.

For more details on n8n expressions in general, you might want to check the Expressions documentation.