The blur event fires when an element has lost focus. The event does not bubble, but the related focusout event that follows does bubble.
An element will lose focus if another element is selected. An element will also lose focus if a style that does not allow focus is applied, such as hidden, or if the element is removed from the document — in both of these cases focus moves to the body element (viewport). Note however that blur is not fired when a focused element is removed from the document.
The opposite of blur is the focus event, which fires when the element has received focus.
The blur event is not cancelable.
Use the event name in methods like addEventListener(), or set an event handler property.
addEventListener("blur", (event) => {});
onblur = (event) => {};
This interface also inherits properties from its parent UIEvent, and indirectly from Event.
FocusEvent.relatedTarget-
The element receiving focus, if any.
HTML
<form id="form">
<label>
Some text:
<input type="text" placeholder="text input" />
</label>
<label>
Password:
<input type="password" placeholder="password" />
</label>
</form>
JavaScript
const password = document.querySelector('input[type="password"]');
password.addEventListener("focus", (event) => {
event.target.style.background = "pink";
});
password.addEventListener("blur", (event) => {
event.target.style.background = "";
});
Result
There are two ways of implementing event delegation for this event: by using the focusout event, or by setting the useCapture parameter of addEventListener() to true.
HTML
<form id="form">
<label>
Some text:
<input type="text" placeholder="text input" />
</label>
<label>
Password:
<input type="password" placeholder="password" />
</label>
</form>
JavaScript
const form = document.getElementById("form");
form.addEventListener(
"focus",
(event) => {
event.target.style.background = "pink";
},
true,
);
form.addEventListener(
"blur",
(event) => {
event.target.style.background = "";
},
true,
);
Result
The value of Document.activeElement varies across browsers while this event is being handled (Firefox bug 452307): IE10 sets it to the element that the focus will move to, while Firefox and Chrome often set it to the body of the document.