Always use explicit null and undefined checks instead of relying solely on optional chaining, especially when you need predictable boolean results or want to prevent null/undefined values from propagating to APIs, URLs, or causing runtime errors.

Use explicit checks with logical operators to ensure clean boolean results:

// Preferred: explicit check ensures boolean result
const isPlatformUser = redirectUrl && redirectUrl.includes("platform") && redirectUrl.includes("new");

// Avoid: optional chaining can return undefined, making isPlatformUser potentially undefined
const isPlatformUser = redirectUrl?.includes("platform") && redirectUrl?.includes("new");

Provide defensive fallbacks for arrays and objects that might be null/undefined:

// Safe array access with fallback
const schedule = (atomSchedule.schedule || []).map(avail => ({
  startTime: new Date(avail.startTime),
  endTime: new Date(avail.endTime),
  days: avail.days,
}));

// Prevent undefined values in object spreads
query: {
  slug: ctx.query.user,
  ...(ctx.query.orgRedirection !== undefined && { orgRedirection: ctx.query.orgRedirection }),
}

Check for both null and undefined when the distinction matters:

// Comprehensive check for functions that don't accept null
if (value !== undefined && value !== null) {
  return decodeURIComponent(value);
}

This approach prevents runtime errors, ensures predictable data types, and makes your code’s null-handling behavior explicit and intentional.

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