JavaScript evaluation

Run a JavaScript expression in a page and get the result back. Evaluation is off by default. Two checks must both pass:

1. The caller holds javascript:evaluate.
2. The session was created with executionPolicy.javascriptEvaluation = true.

Otherwise the call fails with policyDenied.

Evaluate

Create a session with the policy on:

{"name": "workflow_start", "arguments": {"profile": "default", "url": "https://example.com", "executionPolicy": {"javascriptEvaluation": true}}}

Then call the tool:

{"name": "evaluate_javascript", "arguments": {"workflowHandle": "wf_0123456789abcdef0123456789abcdef", "expression": "document.title", "timeoutMs": 5000}}

Set awaitPromise: true to wait for a returned promise. Over HTTP, submit a primitive command with kind: "evaluateJavaScript" and the same input.

Limits

The command class is Reconciliable. Evaluation is not available on the Firefox companion engine; use Chromium for it.