Define custom functions

Flux’s functional syntax lets you define custom functions. Learn the basics of creating your own functions.

On this page:

Function definition syntax

The basic syntax for defining functions in Flux is as follows:

// Basic function definition syntax
functionName = (functionParameters) => functionBody
  • functionName: Name to use to execute the function.
  • functionParameters: Comma-separated list of parameters passed into the function.
  • functionBody: Operations on function parameters.

Define parameter defaults

Use the = assignment operator to assign a default value to function parameters in your function definition:

functionName = (param1=defaultVal1, param2=defaultVal2) => functionBody

Defaults are overridden by explicitly defining the parameter in the function call. Parameters without default values are considered required parameters.

Custom function examples

Square a number

Multiple two values

Calculate n to the p power (with default parameters)

Create a custom transformation

A transformation is a function that takes a stream of tables as input, operates on the input, and then outputs a new stream of tables.

The pipe-forward operator (|>) pipes data from the previous identifier or function forward into a transformation. To use piped-forward data, assign a function parameter to the pipe-receive operator (<-).

In the following example, the function x() receives piped-forwarded data and assigns it to the t parameter. In the function body, t is piped forward into other operations to generate output.

x = (t=<-) => t |> //...

Custom transformation examples

Multiply values by x

Calculate speed

Define functions with scoped variables

To create custom functions with variables scoped to the function,

  1. Enclose your function body in a block ({}).
  2. Use a return statement to return a specific variable.
functionName = (param) => {
    exampleVar = "foo"

    return exampleVar

Example functions with scoped variables

Return an alert level based on a value

Convert a HEX color code to a name

Was this page helpful?

Thank you for your feedback!

Upgrade to InfluxDB Cloud or InfluxDB 2.0!

InfluxDB Cloud and InfluxDB OSS 2.0 ready for production.