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Run script

Run a small JavaScript snippet that can read and change variables.

Where
+ Add actionSystemRun script
Wait
Has a Wait switch: on, the next action starts once this one is done
Run script with a snippet that counts deaths in a shared variable and returns a message. The result is saved to the variable message, and the Run test result is shown below the code.

Run script is the glue between actions. When a condition is not enough, a few lines of JavaScript can do maths, format text, pick a value out of a JSON answer or keep a counter.

Settings

Section titled “Settings”
Setting What it does
Code The JavaScript to run.
Save result to Stores the result in this variable.
Scope This run or Everywhere, see variables.
Run test Runs the snippet now and shows the result, how long it took and which shared variables it would change.

What the script sees

Section titled “What the script sees”
Name Contains
vars.name Every variable the macro can see: the trigger values, shared variables and this run’s variables (this run’s win over shared ones).
globals.name Only the shared variables.
velocity, velocity01, pressure, pressure01, x, y The trigger values, as numbers.
pageId The page of the button, as text.

All variables are text. Turn them into numbers before doing maths: Number(vars.count) + 1.

How it runs

Section titled “How it runs”
  • The result is the value of the last expression, or what you return. As soon as the word return appears anywhere in the code, even in a comment or a string, the snippet runs as a function body, so it needs an explicit return to have a result.
  • Assigning vars.name = ... sets a variable for this run. Assigning globals.name = ... sets a shared variable.
  • Text results are saved as they are, whole numbers without decimals, objects and arrays as JSON. No result saves an empty text.
  • The snippet runs in a sandbox: plain JavaScript without a console, network or file access. Loops stop after 2,000,000 rounds and nesting after 256 calls, so a runaway loop ends with an error instead of hanging Lunchpad.
  • An error is noted in the log and the macro goes on. The Save result to variable is not changed.
  • With Wait on, the next actions see the result and the changed variables.

Examples

Section titled “Examples”

A death counter that says something useful (shared variable deaths, result saved to message):

globals.deaths = Number(globals.deaths || 0) + 1;
return globals.deaths === 1 ? "First death!" : `Death number ${globals.deaths}`;

Pick a value out of an HTTP request answer saved as weather:

return JSON.parse(vars.weather).main.temp > 25 ? "hot" : "fine";
Section titled “Related”