modernize-ecmascript

modernize-ecmascript is a skill for Claude Code, Codex from bosens-China/tc39-atlas. It costs 130 tokens per session (3,082 once invoked), scanned A, original, MIT.

A guide for writing or reviewing JavaScript and TypeScript using newer ECMAScript language features. ECMAScript is the standard behind JavaScript, and the guide checks whether the project's tools and target browsers or runtimes can handle each feature.

In plain words
What is it for?
Use it to modernise selected code, assess whether a JavaScript feature is safe to adopt, and account for the project's compiler, conversion settings, output target, and runtime support.
Why use it?
It prevents newer syntax or built-in APIs from being used where the project's parser, build process, or runtime cannot support them. It focuses changes on code that is actually being written or edited.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it to modernise selected code, assess whether a JavaScript feature is safe to adopt, and account for the project's compiler, conversion settings, output target, and runtime support.

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Install with agentmods
npx agentmods add skills/bosens-china/tc39-atlas/modernize-ecmascript
Install

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.

Any agent
npx skills add bosens-China/tc39-atlas --skill modernize-ecmascript
Clone the repo
git clone --depth 1 https://github.com/bosens-China/tc39-atlas

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for modernize-ecmascript

README.md
[![agentmods](https://agentmods.dev/badge/skills/bosens-china/tc39-atlas/modernize-ecmascript/github.svg)](https://agentmods.dev/skills/bosens-china/tc39-atlas/modernize-ecmascript)
Your own site
<a href="https://agentmods.dev/skills/bosens-china/tc39-atlas/modernize-ecmascript"><img src="https://agentmods.dev/badge/skills/bosens-china/tc39-atlas/modernize-ecmascript/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.

agentmods 80×15 button for modernize-ecmascript

Your own site · 80×15
<a href="https://agentmods.dev/skills/bosens-china/tc39-atlas/modernize-ecmascript"><img src="https://agentmods.dev/badge/skills/bosens-china/tc39-atlas/modernize-ecmascript.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 130 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,082 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00130 $0.03082
Opus 5 $0.00065 $0.01541
Sonnet 5 $0.00026 $0.00616
Haiku 4.5 $0.00013 $0.00308

Measured 10d ago against content hash f70f75be441f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

modernize-ecmascript 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 10d 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.

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.

.agents/skills/modernize-ecmascript/SKILL.md · 145 lines

How it starts

The opening of the file, as written. The whole thing — 145 lines — stays where its author put it; the contents beside it link to each section on GitHub.

现代化 ECMAScript

围绕源码转换链选择能减少代码或明确意图,且不改变可观察行为的 ECMAScript 能力。不要根据框架名称、单一工具版本或一个笼统的“ES20xx 支持”直接得出兼容性结论。

选择一种工作模式

按任务意图依次判断,只选择一种模式:

  1. 存在审查、批量寻找或仓库级简化意图时,选择显式代码审查;用户提供的环境和 ES 约束作为审查条件。
  2. 否则,用户明确提供环境、输出版本、ES 版本,或者指定具体语法或 API 时,选择用户定向编写或能力咨询
  3. 否则,编写或修改 JavaScript、TypeScript 时选择日常语法辅助

手动指定本 Skill 只强制加载工作流,不覆盖更具体的任务意图。

日常语法辅助

  • 只关注当前任务中新写、正在修改或已经触及的代码区域。
  • 不扫描未触及代码,不自动纳入任务开始前已有的 Git 工作区改动。
  • 先判断本次改动是否会产生或改变运行时代码。只涉及类型注解、接口、类型别名、泛型或 .d.ts 等编译后擦除内容,且任务不涉及构建配置或运行时行为时,静默结束现代化判断并继续原任务。
  • 对运行时代码先在当前改动区域识别能减少代码、明确意图或避免手写辅助逻辑的可信候选。没有候选时直接继续原任务;不要仅因 Skill 已触发就读取年度文件、llms.txt 或完整转换链。
  • 形成候选后再从目标文件定位实际解析器、转换器和输出目标,只自动采用能被解析并安全转换的 Stage 4 语法。
  • 语法会保留在产物中时,只有存在明确的目标运行时支持证据才采用。
  • 区分纯语法和运行时敏感能力。只要能力依赖新的标准内置 API、全局对象、协议、polyfill 或 shim,即使表面上包含新语法,也按运行时敏感能力处理;日常模式默认不自动采用。
  • 用户要求最小改动、只修当前问题或不要重构时,可以让本次新写代码采用安全语法,但不为现代化额外改写既有代码。
  • 转换链、输出目标或必要运行时证据缺失、冲突或含糊时,静默停止现代化判断并继续原任务。不要询问用户,也不要在最终汇报中重新说明跳过原因。
  • 不为了展示新语法而改写相邻旧代码。

用户定向编写或能力咨询

  • 以用户给出的范围、目标环境、输出版本、ES 版本和具体能力要求为主。
  • 用户只询问某项能力能否使用时,只调查并回答,不修改代码,也不扩大为仓库级审查;只有用户明确要求编写、应用或改造时才修改请求范围内的代码。
  • 完成安全的自动发现后,目标运行时、输出目标或消费者约束仍然缺失且确实影响结论时,把相关缺失项合并为一次询问,不猜测也不套用日常模式的静默规则。
  • 验证实际解析器和转换器能否处理用户要求的语法,不用仓库默认值静默覆盖用户要求。
  • 要求与工具链冲突时,展示证据和可行选项,请用户确认调整语法、升级或配置转换器、提高输出基线,或者放弃该能力。
  • 用户明确要求标准内置 API 时,额外验证目标运行时或已配置的 polyfill。需要新增 polyfill、shim、转换插件或依赖时,说明来源、影响和替代方案并取得确认。
  • 用户可以明确批准兼容性、构建配置、依赖或实验能力的变更;确认只授权所选方案,不把无法解析或无法转换的能力变成可用能力。
  • 不因定向编写自动扩大为仓库级审查。

显式代码审查

  • 扫描用户指定的文件、包或仓库范围,不受当前修改区域限制。
  • 先定位旧语法、手写辅助逻辑和其他待验证候选,再发现相关源码转换链和输出目标并过滤安全能力。
  • 环境、输出目标或消费者范围缺失且确实影响结论时,完成所有安全发现后集中询问用户。
  • 在问题中给出已检测环境、确切不确定项、可行选项、各自影响和推荐选择,不按候选逐次打断。
  • 用户只要求审查时只输出分析;明确要求应用审查结果时再修改代码。

按 ECMAScript 年份读取能力速览

用户指定一个或多个 ES 版本,或者询问某个版本新增了什么时,先读取对应年度文件。年度文件直接列出该版本的提案、当前 Stage、状态、作用摘要和线上 Markdown;不要为了查一个年份先加载全部提案。日常模式只有形成相关候选后才读取对应年度文件,不把年度摘要作为编码任务的预加载资料。

Read the full file on GitHub · 145 lines

Changes

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.

  1. 10d ago First seen · 145 lines · 130 tokens per session scan A f70f75be441f

Subscribe to this mod's changes

modernize-ecmascript is a skill published in the GitHub repository bosens-China/tc39-atlas (0 stars, last pushed yesterday), licensed MIT. It adds 130 tokens to every session and 3,082 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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