javascript

A teaching guide for JavaScript, the programming language used in web browsers and also on servers through environments such as Node.js.

In plain words
What is it for?
Learning variables, arrow functions, objects, arrays, and other JavaScript basics while working with JavaScript, JSX, or TypeScript files.
Why use it?
It explains common JavaScript syntax in simple terms, helping people understand code generated during rapid, conversational development.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/wewpellex21/code-sensei/javascript
Any agent
npx skills add wewpellex21/code-sensei --skill javascript
Clone the repo
git clone --depth 1 https://github.com/wewpellex21/code-sensei

Made for: Claude Code, Codex.

Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 670 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00038 $0.00670
Opus 5 $0.00019 $0.00335
Sonnet 5 $0.00008 $0.00134
Haiku 4.5 $0.00004 $0.00067

Measured yesterday against content hash 9a4b559a1c78, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

javascript 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.

Origin

This is a copy

100% identical to javascript — 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.

skills/javascript/SKILL.md · 54 lines

How it starts

The opening of the file, as written. The whole thing — 54 lines — stays where its author put it; the contents beside it link to each section on GitHub.

JavaScript — CodeSensei Teaching Module

What is JavaScript?

  • Analogy: If HTML is the skeleton and CSS is the skin, JavaScript is the brain and muscles. It makes things HAPPEN — clicks, animations, data loading, form validation.
  • Key insight: JavaScript runs in the browser (frontend) AND on the server (backend with Node.js). Same language, two different environments.

Core Concepts to Teach (in order of frequency during vibecoding)

const / let / var

  • const = a constant, can't be reassigned (use this most of the time)
  • let = a variable that can change
  • var = the old way, avoid it (mention only if Claude uses it)
  • Quiz: "Why did Claude use const instead of let here?"

Arrow Functions () => {}

  • Analogy: A shorthand recipe card. Instead of writing "Function: do this thing," you write "=> do this thing"
  • This is the #1 syntax that confuses beginners. Normalize it early.

Objects {}

  • Analogy: A filing cabinet with labeled drawers. Each drawer (property) has a name and contains something.
  • { name: "Juan", age: 25 } — the object has two "drawers"

Arrays []

  • Analogy: A numbered list. Items have positions (starting from 0, not 1!)
  • .map(), .filter(), .forEach() — the "assembly line" methods

Async/Await

  • Analogy: Ordering food at a restaurant. You place the order (await) and the kitchen works on it while you chat. When it's ready, it arrives. You don't stand at the kitchen door waiting.
  • Key insight: Some things take time (loading data, saving to database). await means "wait for this to finish before moving on."

Import/Export

  • Analogy: Sharing tools between workshops. export puts a tool in the shared toolbox. import grabs it from there.
  • Key insight: This is how code is organized into separate files that work together.

Template Literals `Hello ${name}`

  • Analogy: Mad Libs — the backtick string has blanks (${}) that get filled in with real values.

Read the full file on GitHub · 54 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. yesterday First seen · 54 lines · 38 tokens per session scan A 9a4b559a1c78

Subscribe to this mod's changes

javascript is a skill published in the GitHub repository wewpellex21/code-sensei (3 stars, last pushed 3d ago), licensed MIT. It adds 38 tokens to every session and 670 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to javascript, differing in 0 lines, and is treated as a copy.

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