Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/0xdarkmatter/claude-mods/javascript-opsnpx skills add 0xDarkMatter/claude-mods --skill javascript-opsgit clone --depth 1 https://github.com/0xDarkMatter/claude-modsWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00077 | $0.03078 |
| Opus 5 | $0.00039 | $0.01539 |
| Sonnet 5 | $0.00015 | $0.00616 |
| Haiku 4.5 | $0.00008 | $0.00308 |
Grade A, and why
javascript-ops scanned grade A with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
const res = await fetch(url, { signal }); Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
| `node:child_process` | Subprocess execution | How it starts
The opening of the file, as written. The whole thing — 286 lines — stays where its author put it; the contents beside it link to each section on GitHub.
JavaScript Operations
Comprehensive reference for modern JavaScript and Node.js — async patterns, module systems, runtime internals, and ES2022-2025 features.
Async Decision Tree
What are you doing asynchronously?
│
├─ Simple one-off operation (DB query, HTTP call)
│ └─ async/await with try/catch ✓ default choice
│
├─ Multiple independent operations
│ ├─ All must succeed → Promise.all([a(), b(), c()])
│ ├─ Don't care about failures → Promise.allSettled([...])
│ └─ First one wins → Promise.race([...]) or Promise.any([...])
│
├─ Need external resolve/reject control (deferred)
│ └─ Promise.withResolvers() (ES2024)
│
├─ Processing a sequence of async values
│ ├─ Known array → for...of with await inside loop
│ └─ Unknown/infinite sequence → async generator + for await...of
│
├─ Large data / backpressure concerns
│ └─ Streams (ReadableStream / node:stream)
│ ├─ Transform data in flight → TransformStream / Transform
│ └─ Pipe chain → stream.pipeline() (Node) / pipeThrough() (Web)
│
├─ CPU-intensive work (would block event loop)
│ ├─ Short burst → offload with setTimeout(fn, 0) to yield
│ └─ Real work → Worker (browser) / worker_threads (Node)
│ └─ Shared memory needed → SharedArrayBuffer + Atomics
│
└─ Legacy code uses callbacks
└─ Wrap with util.promisify() (Node) or new Promise() constructor
Module System Decision Tree
Which module system should I use?
│
├─ New project / Node 18+
│ └─ ESM (set "type": "module" in package.json)
│ ├─ import / export syntax
│ ├─ Top-level await supported
│ └─ Better tree-shaking with bundlers
│
├─ Publishing a library
│ ├─ ESM-only → simplest, but breaks older CJS consumers
│ ├─ CJS-only → safe but no tree-shaking
│ └─ Dual package (recommended) → "exports" field with conditions
│ ├─ "import": "./dist/index.mjs"
│ └─ "require": "./dist/index.cjs"
│
├─ Existing CJS project, want ESM
│ ├─ Per-file migration → rename to .mjs, update require → import
│ ├─ Whole-project → add "type": "module", rename .cjs exceptions
│ └─ Keep CJS, add ESM wrapper → create thin .mjs re-export layer
│
├─ Browser (no bundler)
│ └─ Native ESM — <script type="module"> + importmap
│
└─ Need dynamic loading
└─ import() — works in both ESM and CJS files
├─ Lazy routes / code splitting
└─ Conditional platform code
What ships with it
7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 286 lines · 77 tokens per session scan A f2587724d31b
javascript-ops is a skill published in the GitHub repository 0xDarkMatter/claude-mods (32 stars, last pushed 9d ago), licensed MIT. It adds 77 tokens to every session and 3,078 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 2 findings (makes network calls, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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