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JavaScript value is not a constructor

TypeError: x is not a constructor

JavaScript tried to instantiate a value with new, but that value is not constructable.

TypeError: x is not a constructorruntime

Observed message

TypeError: x is not a constructor

Why it happens

  • New is being used on a function or value that is not constructable.
  • An import or require returned a different value than expected.
  • A method or object property was mistaken for a class or constructor.

How to fix it

  1. Log the value you are calling with new and confirm its actual type.
  2. Check module imports and default-vs-named import usage.
  3. Only use new with classes or constructable functions.

Official reference

MDN: TypeError: x is not a constructor

Related errors

ReferenceError: can't access lexical declaration before initializationJavaScript accessed a let or const binding before initializationReferenceError: assignment to undeclared variableJavaScript assigned to an undeclared variableTypeError: class constructors must be invoked with 'new'JavaScript class constructor was called without newRangeError: x can't be converted to BigInt because it isn't an integerJavaScript could not convert a non-integer value to BigInt

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JavaScript x is not a constructor: causes and fixes | Error Atlas