MIT License: © 2025 Alexander (Soviet9773Red)
JavaScript compatibility and runtime diagnostics tool for Shelly Gen2 / Gen3 / Gen4 devices.
This script performs a controlled set of syntax and API tests to determine which parts of ES5 / ES6 are actually supported by the built-in Shelly JavaScript engine (MJS), which features are only declared, and which are completely missing.
Shelly Script Engine is not a full ES6 environment.
Official documentation describes this only partially, which leads to trial-and-error development.
ES6compShellyTest provides:
- reproducible compatibility results
- structured JSON output for automation
- compact HTML UI for manual inspection
- safe execution within Shelly memory and HTTP limits
- Tests 70+ JavaScript features
- syntax (
let,const, arrow, class, spread, destructuring) - Array / Object / String APIs
- Date, Math, Number APIs
- Promise, Symbol, BigInt
- TypedArrays / ArrayBuffer
- syntax (
- Each feature classified as:
- OK - works correctly
- Declared - identifier exists but not implemented
- Missing - throws error
- Safe
eval-based execution with error classification:- SyntaxError
- ReferenceError
- TypeError
- Automatic device detection via RPC:
- model
- device id
- firmware
- MAC
- Split JSON endpoints to stay below 4 KB HTTP body limit
- GZIP-compressed HTML + JS UI served directly from Shelly
- Console output with ready-to-click endpoint URLs
Based on the number of successful tests, the script estimates approximate ECMAScript level:
ECMAScript 3–5 (1999–2009)ECMAScript 5 + partial ES6 (2015)ES6-level feature coverage(rare on Shelly)
This is an estimation, not a standards conformance claim.
Results are split into three parts to avoid response overflow:
/script/<id>/es6a
/script/<id>/es6b
/script/<id>/es6c
Each endpoint returns:
{
"t": 71,
"p": "A",
"r": [
{ "f": "Array.map()", "s": "OK", "sup": 0 }
]
}t – total number of tested features
p – report segment identifier (A, B, C)
r – array of test results
f – feature name
s – execution status (OK/NO)
sup – error/support code (0 = OK, 1–9 = error type)
This JSON format is intended for diagnostic purposes only. It is optimized for Shelly runtime and HTTP limitations and should not be treated as a stable API contract. The structure may change between versions.
Interactive HTML table rendered directly from Shelly:
/script/<id>/test
Assets are delivered via GZIP-compressed base64 payloads:
/test- HTML/test.js- JavaScript logic
No external hosting required.
On startup the script prints:
- device information (when RPC available)
- detected IP address
- full list of endpoint URLs
- compact test summary
Example:
HTML -> http://192.168.1.45/script/2/test
Splitted JSON endpoints:
Part A -> http://192.168.1.45/script/2/es6a
Part B -> http://192.168.1.45/script/2/es6b
Part C -> http://192.168.1.45/script/2/es6c
Shelly Scripting vs JS Features test v. 1.85 Done.
- Open Shelly Web UI
- Go to Scripts
- Add new script
- Paste content of
ES6compShellyTest v1.85 - Save and start the script
- Open printed URLs in a browser
- Shelly Plus series (Gen2)
- Shelly Pro series (Gen3)
- Firmware >= 1.6 recommended
- Not a performance benchmark
- Does not measure memory fragmentation
- Not a full JS conformance test
- Results may vary slightly across firmware versions
- Verify which JS features are safe to use
- Decide between ES5 and ES6 syntax
- Build portable scripts across Shelly models
- Validate assumptions before refactoring code
- Educational diagnostics for Shelly scripting workshops
Result:
MIT License
Developed by Alexander
project initiated during Shelly Scripting Advanced – October 2025
Project context:
- real-device testing
- memory-constrained runtime
- practical Shelly automation development
Assisted by GPT-based tooling for analysis and documentation.