target and currentTarget

In Javascript, when dealing with events, understanding the distinction between target and currentTarget properties of the event object is fundamental to properly managing event flows, especially in complex applications with nested elements.

"target" Property

• The target property refers to the element that originally triggered the event. It is the element where the eent actually happended, which can be crucial for understanding the context of an event in a user interface.
• For example, if you have a button inside a form and the user clicks on the button, the target property of the click event will be the button itself, regardless of any event listeners that might be triggered along the event propagation path.

"currentTarget" Property

• The currentTarget property, on the other hand, refers to the element to which the event listener has been attached. This property is particularly useful when the same event handler is being used for multiple elements, or when dealing with events in a more complex, nested structure.
• For instance, if the same click event listener is set up to handle clicks on several buttons within a form, currentTarget would refer to the button that was clicked in each case, assuming that the listener is attached directly to each button.

Example

Here's a practical example to illustrate the difference:

document.querySelector('#parent').addEventListener('click', function(event) {
    console.log('target:', event.target.id);      // Could log 'child' if the child was clicked
    console.log('currentTarget:', event.currentTarget.id);  // Will always log 'parent'
});
 
<div id="parent">
    <button id="child">Click me</button>
</div>

In this code, if you click on the button with the id of 'child', event.target would be the button ('child'), because that's where the click event originated. However, event.currentTarget would be the 'parent' div, as that is where the event listener was actually attached.

Understanding the difference between target and currentTarget is essential for property handling events in Javascript, especially in application that utilize event delegation or need to manage events in a dynamic, nested environment. This knowledge allows you to write event handlers that are more flexible and easier to maintain, especially in complex applications where elements interact in varied and nested ways.