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Js Early Exit

Source: .agents/references/coding-standard/vercel-react-best-practices/rules/js-early-exit.md

Metadata​

  • title: Early Return from Functions
  • impact: LOW-MEDIUM
  • impactDescription: avoids unnecessary computation
  • tags: javascript, functions, optimization, early-return

Content​

Early Return from Functions​

Return early when result is determined to skip unnecessary processing.

Incorrect (processes all items even after finding answer):

function validateUsers(users: User[]) {
  let hasError = false
  let errorMessage = ''
  
  for (const user of users) {
    if (!user.email) {
      hasError = true
      errorMessage = 'Email required'
    }
    if (!user.name) {
      hasError = true
      errorMessage = 'Name required'
    }
    // Continues checking all users even after error found
  }
  
  return hasError ? { valid: false, error: errorMessage } : { valid: true }
}

Correct (returns immediately on first error):

function validateUsers(users: User[]) {
  for (const user of users) {
    if (!user.email) {
      return { valid: false, error: 'Email required' }
    }
    if (!user.name) {
      return { valid: false, error: 'Name required' }
    }
  }

  return { valid: true }
}