event listener for element lost focus

Event Listener for Element Lost Focus#

As a web developer, you may often need to perform some action when a user clicks outside of a certain element, such as a form field or a dropdown menu. This can be achieved with the help of an event listener for element lost focus.

Using the blur() method#

The simplest way to add an event listener for element lost focus is by using the blur() method. This method is called when an element loses focus, either by the user clicking outside of it or by the element losing focus programmatically.

const inputField = document.querySelector('#myInput');

inputField.addEventListener('blur', () => {
  // Perform some action when the input field loses focus
});

In the above example, we add an event listener for the blur event to an input field with the ID of myInput. When the input field loses focus, the anonymous function inside the event listener will be called and we can perform some action, such as validating the input or updating a database.

Using the focusout event#

The focusout event is similar to the blur event, but it also triggers when an element's descendants lose focus. This can be useful in some cases, but it also means that the event can be triggered more often than necessary.

const inputField = document.querySelector('#myInput');

inputField.addEventListener('focusout', () => {
  // Perform some action when the input field or its descendants lose focus
});

Using event delegation#

If you have a list of elements that need to trigger an event when they lose focus, you can use event delegation to add a single event listener to a parent element. This can improve performance and reduce the amount of code you need to write.

const list = document.querySelector('#myList');

list.addEventListener('blur', (event) => {
  const listItem = event.target;

  // Perform some action when the list item loses focus
});

In the above example, we add an event listener for the blur event to a parent element with the ID of myList. When a list item loses focus, the event will bubble up to the parent element and we can use event.target to get a reference to the list item that triggered the event. We can then perform some action, such as updating a database or highlighting the selected item.