Modern JavaScript Core
When to use this skill
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Writing vanilla JavaScript logic.
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Understanding modern syntax in PR reviews.
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Avoiding legacy patterns (var, callbacks).
- Essential Syntax
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Variables: const by default, let if reassignment is needed. Never var .
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Functions: Arrow functions () => {} for callbacks and lexical this .
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Destructuring: Use generously (const { id, name } = user ).
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Template Literals: Use backticks for string interpolation.
- Async Patterns
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Async/Await: Prefer over .then() chains.
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Top-level Await: Supported in modern modules.
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Promise.allSettled: Better for unrelated concurrent tasks than Promise.all (which fails fast).
- Modules
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ES Modules: import /export syntax is standard.
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Named Exports: Prefer named exports (export const foo ) over export default for better refactoring support.
- Modern Array Methods
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Usage: map , filter , reduce , find , some , every .
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Newer: floated (toSorted), toSpliced (immutable alternatives).