Table of Contents


Block Group: Logic
Icon:Trace block icon

Monitors changes to specified properties and logs changes in the browser's JavaScript console. This block is useful for debugging dataflow. It logs changes using the following syntax:

Trace: <timestamp> : <traceLabel> : <property path> : <msg> : <value>

The traceLabel and msg portions appear only if those properties are defined.

For information on using dataflow blocks, see Dataflow.

Input/Output Properties

These properties can take input and give output.

  • tracing (boolean)
  • msg (string)
  • input n

tracing specifies whether the changes are recorded. In addition to TRUE and FALSE, you can also set a value of Auto.

Tips: Setting the tracing Value to Auto

  • The default value is Auto when you add a new Trace block.
  • You can also make the value Auto by mousing over the property, clicking the blue dot, and selecting Reset.
  • An Auto value looks like a False value, with two differences: if the value is Auto, then when you hover over the property, the blue dot is not filled in, and when you click the blue dot, there is no Reset option.
  • TRUE: Changes are logged in the console.
  • FALSE: Changes are not logged.
  • Auto: Changes are logged only if the Advanced property traceLabel is not null for the Stage.

msg specifies a string to be included in the developer console when values for this block are updated.

input n specifies the path to one of the properties that this block monitors.


This is a basic use of the block.

Dataflow ModelDescription
Trace dataflow modelEach log message in the console includes the value of msg ("AAAA") and also the Stage's value of traceLabel ("BBBB").