Either you attempted to invoke one of the Function prototype methods on an object that was not a Function object, or you used an object in a function call context. For example, the following code produces this error because example is not a function.

var example = new Object();  // Create a new object called "example".
var x = example();           // Try and call example as if it were a function.

To correct this error

• Only call Function prototype methods on Function objects.
• Ensure that you use the function call operator () to call functions only.

See Also

Function Object | prototype Property