Best Practices and Optimization | JavaScript Lesson

Lesson content

Read, practise, then check your understanding

Use modules, small functions, clear ownership, const by default, strict equality, explicit validation, and semantic DOM APIs. Avoid hidden globals, prototype modification, implicit coercion at boundaries, swallowed rejections, unsanitized HTML, and unbounded work.

Measure real behavior

export function average(values) {
  if (values.length === 0) return 0;
  return values.reduce((sum, value) => sum + value, 0) / values.length;
}

Profile before optimizing. Improve algorithms and network/database behavior first; then reduce allocation, layout thrashing, bundle size, and main-thread blocking. Debounce bursty input, virtualize large views, cache with invalidation rules, and code-split expensive features. Automate formatting, static analysis, security scanning, and build checks even when repository test cases are intentionally absent.

Knowledge check

Answer every question correctly to complete this chapter.

Which statement best describes strict equality?

Which JavaScript term matches this description: Comparison that avoids coercive equality surprises.

Which statement best describes immutability?

Which JavaScript term matches this description: Avoiding mutation to simplify reasoning and state change.

Which statement best describes profiling?

Which JavaScript term matches this description: Measuring representative runtime behavior before optimization.

Which statement best describes debouncing?

Which JavaScript term matches this description: Delaying repeated calls until activity becomes quiet.

Which statement best describes code splitting?

Which JavaScript term matches this description: Loading application modules in smaller on-demand chunks.

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