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JavaScript tried to call something that is not a function

TypeError: x is not a function

JavaScript attempted to invoke a value as a function, but the value is not callable.

TypeError: x is not a functionruntime

Observed message

TypeError: x is not a function

Why it happens

  • Code calls a non-function value with parentheses.
  • An expected method does not exist on the current value.
  • An import, property access, or refactor changed what the identifier points to.

How to fix it

  1. Log the value before calling it and verify that it is callable.
  2. Check property names, method availability, and prototype assumptions.
  3. Review import shape and default-vs-named exports if the value comes from a module.

Official reference

MDN: TypeError: x is not a function

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 function: causes and fixes | Error Atlas