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3010 errors · 53 languages · Open source

Common Errors

javascript3 fixes

Cannot read property of undefined

Cannot read propert(y|ies) of undefined

  • •Add optional chaining (?.)
  • •Check if object exists before accessing
javascript3 fixes

Cannot read property of null

Cannot read propert(y|ies) of null

  • •Add null check before access
  • •Use optional chaining (?.)
javascript3 fixes

TypeError: X is not a function

is not a function

  • •Check spelling of method name
  • •Verify import is correct
javascript3 fixes

ReferenceError: X is not defined

is not defined

  • •Import or declare the variable
  • •Check for typos in variable name
javascript3 fixes

TypeError: Assignment to constant variable

Assignment to constant variable

  • •Use let instead of const
  • •Create new variable for modified value
javascript3 fixes

TypeError: Cannot assign to read only property

Cannot assign to read only property

  • •Clone object before modifying with spread or structuredClone
  • •Use Object.defineProperty with writable:true