When you write event handlers in JavaScript, understanding how the value of this is set is essential for predicting your code’s behavior. The value of this inside an event handler depends on how the handler function is defined and attached. For event listeners on DOM elements, if you use a regular function expression, this inside the handler refers to the element that received the event. However, if you use an arrow function, this does not refer to the element; instead, it inherits the value of this from the surrounding lexical scope, which is often window or undefined in strict mode. This difference can lead to unexpected results if you try to access properties of the element using this in an arrow function.

A common pitfall is assuming that this always points to the element that triggered the event, regardless of the function type. This is not the case with arrow functions. Therefore, you should use regular functions when you need this to refer to the event target element, and use arrow functions only when you intentionally want to inherit this from the parent scope.