Why does `this` not behave as expected in arrow functions within event handling?

Understanding Arrow Function Behavior with Event Handling in Javascript

When utilizing arrow functions as callbacks in event handling, it's important to consider the difference between this and event.currentTarget. In arrow functions, this refers to the context where the function is defined, not where it's used. Therefore, to access the element to which the handler is bound, it's necessary to use event.currentTarget instead of this.

Distinction between event.currentTarget and event.target

Understanding the distinction between event.currentTarget and event.target is crucial in event bubbling and capturing. event.currentTarget represents the element that has the event listeners attached, while event.target denotes the element that initially triggered the event.

According to the documentation: "currentTarget of type EventTarget, readonly. Used to indicate the EventTarget whose EventListeners are currently being processed. This is particularly useful during capturing and bubbling."

Example: Event Propagation with Bubbling and Capturing

In the given code snippet, the difference between using this and event.currentTarget in event handling is illustrated:

<code class="javascript">var parent = document.getElementById('parent');
parent.addEventListener('click', function(e) {

  document.getElementById('msg').innerHTML = "this: " + this.id +
    "<br> currentTarget: " + e.currentTarget.id +
    "<br>target: " + e.target.id;
});

$('#parent').on('click', function(e) {

  $('#jQmsg').html("*jQuery<br>this: " + $(this).prop('id')
                   + "<br>currenTarget: " + $(e.currentTarget).prop('id') 
                   + "<br>target: " + $(e.target).prop('id'));
});

$('#parent').on('click', e => $('#arrmsg').html('*Arrow function <br> currentTarget: ' + e.currentTarget.id));</code>

When an event occurs, it propagates through the DOM, starting from the target element and moving up the tree to the root. During this process, the event.target indicates the element that triggered the event at each level, while event.currentTarget represents the element that has the event listener attached to it.

Summary

To ensure proper event handling with arrow functions, it's essential to understand the distinction between this and event.currentTarget. Using event.currentTarget allows you to access the element associated with the event listener, regardless of the context in which the arrow function is defined.

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