The onblur property of the GlobalEventHandlers mixin is the event handler for processing blur events. It's available on Element, Document, and Window.
The blur event is raised when an element loses focus.
Note: The opposite of onblur is onfocus.
target.onblur = functionRef;
functionRef is a function name or a function expression. The function receives a FocusEvent object as its sole argument.
This example uses onblur and onfocus to change the text within an <input> element.
<input type="text" value="CLICK HERE">
let input = document.querySelector('input');
input.onblur = inputBlur;
input.onfocus = inputFocus;
function inputBlur() {
input.value = 'Focus has been lost';
}
function inputFocus() {
input.value = 'Focus is here';
}
Try clicking in and out of the form field, and watch its contents change accordingly.
In contrast to IE, in which almost all kinds of elements receive the blur event, only a few kinds of elements on Gecko browsers work with this event.