JavaScript

Modern JS is expressive and fast — most footguns come from async handling, mutation, and equality/coercion surprises. Prefer clarity and immutability; let the engine optimize.

Language baseline

• const by default, let when reassigning, never var.
• Use ===/!==; avoid == (coercion surprises). Know that NaN !== NaN (use Number.isNaN).
• Prefer pure functions and immutable updates ({...obj}, [...arr], .map/.filter/.reduce) over in-place mutation of shared data.
• Optional chaining ?. and nullish coalescing ?? (distinct from ||, which also catches 0/"").
• Use modules (import/export); no global leakage. Keep imports at the top.
• Prefer for...of / array methods over index loops; Map/Set over object-as-dict for dynamic keys.

Async done right