What does the `this` keyword refer to in the context of a JavaScript function?

In JavaScript, the this keyword is a nuanced topic that depends heavily on how a function is called. When used within a function, this references the object that is currently executing that function or the context in which the function is invoked.

When a function is called as a method of an object, this refers to that object. For example, if you have an object with a method and you call that method on the object, this inside the method will point to the object itself. This behavior allows for dynamic context, enabling functions to operate on different objects without needing to be rewritten.

In strict mode, if a function is called as a standalone function (not attached to any object), this will be undefined. However, if it's called as a method of an object, this will always refer to that object, which is critical for methods that need to access object properties or other methods.

Understanding how this behaves in different contexts, such as normal function calls, method calls, and with functions like call, apply, or when bound with .bind(), is essential for mastering JavaScript's object-oriented principles.