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BytesAgain β€Ί Skills β€Ί JavaScript
πŸ¦€ ClawHub

JavaScript

by @ivangdavila

Write robust JavaScript with async patterns, type coercion handling, and modern ES2023+ features.

Versionv1.0.3
Downloads3,733
Stars⭐ 5
#coding#writing#legal#gaming
TERMINAL
clawhub install javascript

πŸ“– About This Skill

name: JavaScript slug: javascript version: 1.0.3 description: Write robust JavaScript with async patterns, type coercion handling, and modern ES2023+ features.

When to Use

User needs JavaScript expertise β€” from core language features to modern patterns. Agent handles async/await, closures, module systems, and ES2023+ features.

Quick Reference

| Topic | File | |-------|------| | Async patterns | async.md | | Type coercion rules | coercion.md | | Array and object methods | collections.md | | Modern ES features | modern.md |

Equality Traps

  • == coerces: "0" == false is true β€” use === always
  • NaN !== NaN β€” use Number.isNaN(), not === NaN
  • typeof null === "object" β€” check === null explicitly
  • Objects compare by reference β€” {} === {} is false

    • this Binding

  • Regular functions: this depends on call site β€” lost in callbacks
  • Arrow functions: this from lexical scope β€” use for callbacks
  • setTimeout(obj.method) loses this β€” use arrow or .bind()
  • Event handlers: this is element in regular function, undefined in arrow (if no outer this)

    • Closure Traps

  • Loop variable captured by reference β€” let in loop or IIFE to capture value
  • var hoisted to function scope β€” creates single binding shared across iterations
  • Returning function from loop: all share same variable β€” use let per iteration

    • Array Mutation

  • sort(), reverse(), splice() mutate original β€” use toSorted(), toReversed(), toSpliced() (ES2023)
  • push(), pop(), shift(), unshift() mutate β€” spread [...arr, item] for immutable
  • delete arr[i] leaves hole β€” use splice(i, 1) to remove and reindex
  • Spread and Object.assign are shallow β€” nested objects still reference original

    • Async Pitfalls

  • Forgetting await returns Promise, not value β€” easy to miss without TypeScript
  • forEach doesn't await β€” use for...of for sequential async
  • Promise.all fails fast β€” one rejection rejects all, use Promise.allSettled if need all results
  • Unhandled rejection crashes in Node β€” always .catch() or try/catch with await

    • Numbers

  • 0.1 + 0.2 !== 0.3 β€” floating point, use integer cents or toFixed() for display
  • parseInt("08") works now β€” but parseInt("0x10") is 16, watch prefixes
  • Number("") is 0, Number(null) is 0 β€” but Number(undefined) is NaN
  • Large integers lose precision over 2^53 β€” use BigInt for big numbers

    • Iteration

  • for...in iterates keys (including inherited) β€” use for...of for values
  • for...of on objects fails β€” objects aren't iterable, use Object.entries()
  • Object.keys() skips non-enumerable β€” Reflect.ownKeys() gets all including symbols

    • Implicit Coercion

  • [] + [] is "" β€” arrays coerce to strings
  • [] + {} is "[object Object]" β€” object toString
  • {} + [] is 0 in console β€” {} parsed as block, not object
  • "5" - 1 is 4, "5" + 1 is "51" β€” minus coerces, plus concatenates

    • Strict Mode

  • "use strict" at top of file or function β€” catches silent errors
  • Implicit globals throw in strict β€” x = 5 without declaration fails
  • this is undefined in strict functions β€” not global object
  • Duplicate parameters and with forbidden

    • ⚑ When to Use

    User needs JavaScript expertise β€” from core language features to modern patterns. Agent handles async/await, closures, module systems, and ES2023+ features.