In JavaScript, what must occur for a function to execute?

For a function in JavaScript to execute, it must be both declared and invoked. Function declaration defines the function and how it works, while function invocation is the act of calling that function to perform its specified task. Without the invocation, the function remains defined but does not run.

The requirement for function execution does not include compilation, as JavaScript is an interpreted language, meaning it runs directly in the browser or the JavaScript engine without a compilation step. Return statements are not necessary for a function to execute; a function can run and perform its actions without returning a value. Similarly, having parameters is not a prerequisite for execution; a function can be defined without parameters and still be called and executed. Therefore, the key requirement is that the function must be properly declared and subsequently invoked to carry out its function.