config/doc/probe/js.config.hjson

// This is an example config to be used with the --probe-config switch.
{
  "probes": {
    "js": {
      # You can use "setup" to run some code before any story and set up
      # some tracking or patch existing JS functions.
      # setup: "globalThis.customMetrics = { };"

      # This js code should return a simple JS object where the keys are the
      # metric names and the values are numbers. The data is then automatially
      # merged over multiple iterations by the probe.
      "js": '''return { "elements":  document.getElementsByTagName("*").length };'''
    }
  }
}