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 ncaq/konoka --skill nullish-undefined-nullgit clone --depth 1 https://github.com/ncaq/konokaWrote 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/ncaq/konoka/nullish-undefined-null)<a href="https://agentmods.dev/skills/ncaq/konoka/nullish-undefined-null"><img src="https://agentmods.dev/badge/skills/ncaq/konoka/nullish-undefined-null/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/ncaq/konoka/nullish-undefined-null"><img src="https://agentmods.dev/badge/skills/ncaq/konoka/nullish-undefined-null.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 | $0.00036 | $0.00639 |
| Opus 5 | $0.00018 | $0.00319 |
| Sonnet 5 | $0.00007 | $0.00128 |
| Haiku 4.5 | $0.00004 | $0.00064 |
Grade A, and why
nullish-undefined-null 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 4d 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.
What it actually says
nullよりundefinedを優先して使う
TypeScript/JavaScriptにおいてundefinedとnullが両方あるのは単なる歴史的経緯による混乱なので、
なるべくundefinedだけを使うようにしてください。
nullを使って良い場合
特別なnull
既存のAPIでnullに意味がある場合は許容されます。
例えばReactのコンポーネントが返却するnullは何も描画しないことを表します。
そのように様々な既存のライブラリで、
nullが自然に発生する箇所ではnullのまま扱っても構いません。
undefinedに変換するのは必須ではありません。
「選択の余地がある場合にundefinedを優先する」というポリシーであり、
nullを逐一排除するものではありません。
nullishとの比較には == null / != null を使う
Nullish valueであるundefinedやnullとの比較には、
基本的には、
厳密等価演算子(=== undefined, !== undefined, === null, !== null)ではなく、
抽象等価演算子 (== null, != null) を使ってください。
== nullはundefinedとnullの両方にマッチするため、
どちらか一方のチェック漏れを防げます。
これらを厳密に分ける必要はほぼないはずです。 厳密に分けているインターフェイスはあまり良くないのですが、 既存のインターフェイスがそうであれば仕方がありません。
ESLintのeqeqeqルールがalwaysに設定されていると== nullが警告されますが、
現代の一般的なESLint設定ではsmartオプションが有効になっており、
nullとの比較に==/!=を使うケースは許容されるため基本的に問題ありません。
// 良い例
if (value == null) {
/* value is null or undefined */
}
if (value != null) {
/* value is neither null nor undefined */
}
// 避ける例
if (value === null || value === undefined) {
/* 冗長 */
}
if (value !== null && value !== undefined) {
/* 冗長 */
}
if (value === null) {
/* undefined を見落とす可能性がある */
}
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.
- 4d ago First seen · 64 lines · 36 tokens per session scan A 03310694a7c1
nullish-undefined-null is a skill published in the GitHub repository ncaq/konoka (3 stars, last pushed yesterday), licensed Apache-2.0. It adds 36 tokens to every session and 639 once invoked, about $0.0002 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 2026-09-05.
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