The expression doesn’t evaluate to a function, so it can’t be invoked.

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When the expression doesn’t evaluate to a function, it means that the value stored in the expression is not a function and cannot be invoked or called as a function.

In JavaScript, functions are first-class citizens, meaning they can be stored in variables, passed as arguments to other functions, and returned from functions. However, if the value stored in the expression is not a function, you will encounter an error when trying to invoke it.

Here’s an example to illustrate this:

// Example 1: Function expression
var sayHello = function() {
  console.log('Hello!');
};

sayHello(); // Output: "Hello!"

// Example 2: Assigning a non-function value to the variable
var greetings = 'Hello!';

greetings(); // Error: "greetings is not a function"

In the above examples, we declare a function expression in Example 1 and successfully invoke it. In Example 2, we assign a string value to the variable instead of a function and try to invoke it, which results in an error.

To resolve the error, ensure that the expression you are trying to invoke is indeed a function. Check if the variable or expression stores a function or if you need to reassign it to a valid function before invoking it.

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