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 skills add frontal-labs/mcp-server --skill modern-javascript-patternsgit clone --depth 1 https://github.com/frontal-labs/mcp-serverWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/frontal-labs/mcp-server/modern-javascript-patterns)<a href="https://agentmods.dev/skills/frontal-labs/mcp-server/modern-javascript-patterns"><img src="https://agentmods.dev/badge/skills/frontal-labs/mcp-server/modern-javascript-patterns/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/frontal-labs/mcp-server/modern-javascript-patterns"><img src="https://agentmods.dev/badge/skills/frontal-labs/mcp-server/modern-javascript-patterns.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What 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 5.1 | $0.00064 | $0.00461 |
| Opus 5.5 | $0.00026 | $0.00184 |
| Sonnet 5.5 | $0.00013 | $0.00092 |
| Haiku 4.5 | $0.00006 | $0.00046 |
Grade A, and why
modern-javascript-patterns scanned grade A with 0 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 yesterday.
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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
100% identical to modern-javascript-patterns — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
What it actually says
Modern JavaScript Patterns
Comprehensive guide for mastering modern JavaScript (ES6+) features, functional programming patterns, and best practices for writing clean, maintainable, and performant code.
When to Use This Skill
- Refactoring legacy JavaScript to modern syntax
- Implementing functional programming patterns
- Optimizing JavaScript performance
- Writing maintainable and readable code
- Working with asynchronous operations
- Building modern web applications
- Migrating from callbacks to Promises/async-await
- Implementing data transformation pipelines
Detailed patterns and worked examples
Detailed pattern documentation lives in references/details.md. Read that file when the navigation tier above is insufficient.
Best Practices
- Use const by default: Only use let when reassignment is needed
- Prefer arrow functions: Especially for callbacks
- Use template literals: Instead of string concatenation
- Destructure objects and arrays: For cleaner code
- Use async/await: Instead of Promise chains
- Avoid mutating data: Use spread operator and array methods
- Use optional chaining: Prevent "Cannot read property of undefined"
- Use nullish coalescing: For default values
- Prefer array methods: Over traditional loops
- Use modules: For better code organization
- Write pure functions: Easier to test and reason about
- Use meaningful variable names: Self-documenting code
- Keep functions small: Single responsibility principle
- Handle errors properly: Use try/catch with async/await
- Use strict mode:
'use strict'for better error catching
For common pitfalls (this binding, promise anti-patterns, memory leaks), see references/advanced-patterns.md.
What ships with it
2 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.
- yesterday First seen · 44 lines · 64 tokens per session scan A 32e203b8d944
modern-javascript-patterns is a skill published in the GitHub repository frontal-labs/mcp-server (1 stars, last pushed yesterday), licensed Apache-2.0. It adds 64 tokens to every session and 461 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to modern-javascript-patterns, differing in 0 lines, and is treated as a copy.
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